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Rhizobium Symbiosis with Woody Plants: Leguminous Nitrogen-Fixing Trees

Douglas Barnes’s Articles at Permaculture Reflections, Page 6

February 26, 2009 by Douglas Barnes Leave a Comment

Key points:

  • 3 subfamilies of the legume family can fix nitrogen
  • Symbiotic bacteria (Rhyzobium) convert nitrogen in the air to a form plants can use
  • Repair damaged land in tropical and arid regions with initial plantings of 90% nitrogen fixers

As mentioned in the previous article in this series, beneficial partnerships are the way of nature. In particular, some microbes (Frankia and Rhizobium) form associations with certain plants allowing them to fix atmospheric nitrogen into a form that plants can use. These symbiotic partners can help us to rehabilitate damaged landscapes, preparing the soil for a succession of more long-term plants.

Rhizobium nodule

This piece focuses on woody plants that associate with the bacteria of the genus Rhizobium. We can see from the diagram below that there are 3 subfamilies of the family Fabaceae (AKA Leguminosae). These families are Faboideae (AKA Papilionoideae), Mimosoideae, and Caesalpinoideae. Note that not all the trees in these subfamilies are nitrogen-fixers. Among the Caesalpinioideae, 23% are nitrogen fixers. For Mimosoideae, the figure is 90%, and for Faboideae, 97% are nitrogen-fixers.

Nitrogen fixers using Rhizobium

As the diagram shows, Mimosoideae contains the nitrogen-fixers Acacia, Albizia, Calliandra, Enterolobium, Leucaena, Mimosa, Paraserianthes, and Pithecellobium. Caesalpinoideae‘s nitrogen-fixers are Chamaecrista, Cordeauxia; and Faboideae has Cajanus, Dalbergia, Erythrina, Flemingia, Gliricidia, Pterocarpus, Robinia, Sesbania, and Tephrosia.

To rapidly revegetate a damaged landscape, be sure to include plenty of these species to help quickly build up the soils. In areas of very problematic soil, such as arid, tropical and subtropical regions, make 90% of your initial planting of trees nitrogen fixing, pioneer species (associating with either Frankia or Rhizobium), and 10% of species your long-term canopy overstory species. When the system reaches maturity, the proportions will be reversed with 10% nitrogen-fixing, support species and 90% canopy species. The same formula could be followed for humid temperate regions, but the soils in these area are not so fragile and can stand a lower percentage of nitrogen fixers. A 70/30 or even lower may suffice in these areas, as the seasonal cycles of death and regrowth feed these soils well.

As the diagram below shows, the nitrogen-fixing support trees can be pruned (coppiced, pollarded, shredded or sacrificed) to provide mulch, fodder, fuel or fibre. As this is done, the roots of the tree self-prune, releasing nitrogen into the soil.

Chop and drop

The highest concentrations of nitrogen are to be found in descending order in the seeds, the seed pods, the flowers, the leaves and then the woody parts of the tree. Inter-planting with fruit or nut trees naturally provides more soil nitrogen. But interplanting also makes the job of chop-and-drop mulching that much easier.

Nitrogen-fixing support trees

Filed Under: Article Tagged With: soil, trees

Comfrey

Douglas Barnes’s Articles at Permaculture Reflections, Page 6

February 15, 2009 by Douglas Barnes Leave a Comment

Comfrey (Symphytum officinale). What better plant to feature as Species of the Month than this herbaceous member of the Boraginaceae family?

Comfrey

It grows up to 150 cm tall and 60 cm in diameter in warm climates. The optimum growth is in climates where day and night are equal (i.e. the tropics). There, production of 100 to 200 tons per acre (roughly 250 to 500 metric tons per hectare) is possible! However, it will grow in temperate regions. It prefers full sun and soils rich in nitrogen and humus, so interplanting with nitrogen fixers and mulching is a good idea. You can expect to get at least 10 years out of one plant, and a well-attended plant might outlive you!

Animal Fodder

t is protein rich with 15 to 30% dry-weight protein content, rivalling some legumes. It is used as a pig fodder successfully in amounts up to 80 to 90% of the diet! For poultry, it can reduce the need for other feed (be that your concoction or processed feed) by 50%. Egg quality will improve with yolks being brighter. Cows don’t bloat when eating comfrey like they do with clover. And too much clover can taint the milk – not a problem with comfrey. Also, mastitis is reduced in cows fed comfrey. Wilted comfrey mixed with straw fed to sheep at a ratio of one part comfrey to one and a half parts straw increases the digestion of the straw. The flowers make it useful as bee fodder. It is used in zoos as fodder for many (expensive) animals. Its tremendous production rates make it a great elephant feed.

Soil Improvement

Comfrey has deep roots which are hypothesized to draw up nutrients from subsoils. This characteristic would make it a valuable nutrient cycler. There are claims that it accumulates nitrogen, potassium, phosphorus, calcium, zinc, manganese, magnesium, copper, sodium, sulfur, chromium, molybdenum and lead (the latter might make it useful in cleaning roadside soils contaminated by the use of leaded gasoline). It can be used as a green manure, and its ability to be cut right down to the ground a few times a year helps in this respect. It can be used as a compost activator. For hard evidence, see the article Does Comfrey Really Improve Soil? by Ben Stallings.

It can be made into a liquid plant feed:

Place harvested comfrey in a sealable bucket
Weigh down the comfrey with a stone
Wait 1 or 2 weeks
Drain out the juice and dilute it 10 to 1 with water and water your plants with it

You can also use it to fill niches to suppress weeds.

As Food

Traditionally the whole plant has been used. Young leaves can be added to salads in small quantities to boost nutrient uptake. The stems can be blanched and eaten like asparagus. It is the only known plant source of vitamin B12.

As Medicine

Contains allantoin, which assists in the repair of damaged tissues. It is used as a poultice for cuts, scrapes, burns, skin conditions, ulcers, broken bones, strains and aches. It can help with digestive problems. The juice from leaves can be rubbed into the coats of dogs with mange.

The full catalogue of uses is:

  • Vulnerary (wound healer)
  • Astringent (contracts tissue making it useful to treat bleeding, peptic ulcers, diarrhoea, shrink mucus membranes, etc.)
  • Expectorant (dissolves mucus making it useful in treating phlegm)
  • Emollient (smoothes and softens skin)
  • Demulcent (treats inflamed, irritated tissue by coating it – e.g. treating a dry cough)
  • Antiseptic (helps treat or prevent infection in wounds)
  • Nutritive (along with its protein and minerals, it contains vitamin B1, B2, B3, B5, B6, B12, C, E and 28,000 IU of vitamin A per 100g)
  • Tonic
  • Styptic (helps stop bleeding)
  • Antioxidant (from the rosmarinic acid it contains)

Pest Control

Slugs go for comfrey, so you could use it to attract slugs away from plants. If you really want to go all out against slugs, grow a ring of comfrey around your garden, separating the garden with an electric fence. The comfrey will attract the slugs from the garden. Then run pigs in the comfrey. The pigs will love both the comfrey and the slugs. And the pig urine and manure will attract in even more slugs, hopefully depleting your local population for a while. In place of the pigs, poultry could be run as well.

Caution Needed?

Comfrey does contain pyrrolizidine alkaloids which have the potential for liver damage. There have been warnings put out against the use of the herb, but evidence of incontrovertible documented toxicity is lacking. In the book “The Safety of Comfrey,” J.A. Pembery found no reported cases of pyrrolizidine poisoning from comfrey. He did find one case of pigs in Germany being poisoned by nitrates in comfrey, but not by pyrrolizidine. Lab tests on rats suggest that to cause harm to humans, one would have to eat about 20,000 leaves. Certainly from anecdotal evidence, many people have eaten comfrey without reservations for decades and been very healthy. Still, to err on the side of caution, limit consumption. Also, drying the comfrey reduces the amounts of alkaloids.

Filed Under: Article

The Goals of Permaculture

Douglas Barnes’s Articles at Permaculture Reflections, Page 6

February 2, 2009 by Douglas Barnes Leave a Comment

What are the goals of permaculture design? What are we trying to do? The goal of any design is to provide a solution to a problem. The problem permaculture addresses is the maximization of human welfare achieved in a sustainable way. To put it another way, we are trying to ensure long-term survival in a way that does not make us all miserable.

When the term “sustainable” is used, we are really talking about energy budgeting. In a closed system like the Earth (or even in our finite galaxy) there is a maximum amount of energy available. To be able to survive long term means not spending more than you save. A designed human environment is sustainable if, over its lifetime, it captures more energy than was required for its manufacture, implementation and maintenance and provides a surplus for human use. Considering the current industrial model for food production, in which one calorie of food energy is created at the expense of 10 calories of input energy, this definition shows us that our food systems are not sustainable. Similar accounting for other human activities shows that sustainable activity is actually the exception these days.

Solution?

With the problem defined, we can work out a solution. Keeping sustainability in mind, we can set a guideline for design: Design action around energy, not the other way around. A given bioregion has a limit to how much energy it can capture and store for our activities. To go beyond this limit is to push the costs of those activities off onto others and future generations. We are not interested in a sociopathic approach to design, so we want to avoid doing this outcome.

One way to design around energy is through the permaculture technique of setting up zones for activities. Activities that require regular, daily attention should be located in a place close to where the people are. While I am always pleased to see people producing their own food in gardens, those gardens are unfortunately usually located at the farthest point in the backyard from the backdoor. Incentive to trudge all the way out there is reduced by its relative distance and it requires more human energy to get out there. How likely are you to go out to the garden to pick fresh herbs for your breakfast if it’s raining and the garden is 10 metres or more from the door? Not very likely. As the attention required by the elements in the design decreases, their distance from the most trafficked areas increases. Animals, if they are incorporated into the design, are a little farther out, perhaps with fruiting perennials. Nut and timber trees are farther out still. With elements placed geographically according to frequency of use, the energy required to tend to them is minimized.

To maximize energy efficiency, we can also mimic nature. Living and nonliving elements in ecosystems are interconnected, so should the elements in our design be. While the approach of compartmentalizing each element makes for simplicity in the minds of men, it is unnatural and creates more work than is necessary. One could set up an area for one set of crops, then another set of crops, another for trees, another for poultry, and so on. It looks simple – everything in its place. But to do this is to simultaneously ignore beneficial interactions between elements and to create more work for ourselves. If crops such as onions and others from the lily family are planted with apple trees, for example, they would provide a non-competing groundcover (unlike grasses) and flowers to attract pollinators and a host of other beneficial insects that show up with them. Compartmentalized, however, this mutually beneficial arrangement is lost. Poultry let into the garden in a controlled manner provide pest control, weeding and fertilization with minimal losses of garden vegetables. Poultry under perennial fruits clean up fallen fruit, breaking pest cycles. Separated and compartmentalized, these elements cannot mutually interact and start to generate waste. This means more work is left up to the people on site. We can match up these elements by noting their characteristics and matching them with other needs. Chickens love scratching, for example. Pigs love rooting. If you have either animal, why damage soil life by cultivating the ground with an expensive and unsustainable machine in preparation for a garden when you can pen these animals in to the future garden site to do a better job without hurting the soil life and fertilize the soil at the same time?

We can also make note of harmful interactions as well. For example, some plants, like sunflowers, are allelopathic, meaning they put out a chemical that suppresses the growth of most other plants. While they might not make a beneficial companion for your other plants, they could be used as living barriers to prevent the spread of plants you are growing but don’t want to invade other parts of the garden. Ignoring this use of the characteristics of allelopathic plants means that the gardener must now expend energy to put in some sort of artificial barrier – one that has its own embodied energy cost.

Inorganic elements on site are also a consideration. A sun-facing rock will store heat, for instance, making it sometimes possible to grow plants in the microclimate around it that would otherwise not survive or thrive in that climate.

Returning to the goal of permaculture design – creating sustainable environments to meet human needs – we need to look at just what human needs are. Fortunately, we are the most studied species on the planet. There is plenty of information available on the physiological, social and psychological needs of the species to make a very detailed set of species characteristics. Furthermore, the area of happiness has also been studied showing us what makes us genuinely happy and what does not.

Our physiological needs include clean food, clean water, clean air, warmth, and shelter. The physiological does not stand alone, however. The social and psychological are also a part of the requirements for physical health, though they themselves are intangible.

Maslow’s hierarchy of needs is a pretty good model for determining human needs, and the diagram below is patterned in large part, though not exclusively, from it. I’ve put together some of the needs that I’ve seen have empirical evidence to back them and avoided the influence of spiritual, political or economic ideology as best as I could. For simplicity’s sake, the needs here are not meant to be an exhaustive list of human needs, just a sampling of important needs.

Human needs/species characteristics

Next, we can ask what the aim of the current status quo system is.

Is the aim of our society long term sustainability/survivability? Not by any stretch of the imagination. We are living well beyond our needs with the dream that some wondrous technology will come and solve this problem for us. There is no better recipe for collapse of civilization than that.

Is the aim of our society personal or community happiness? Again, no. We have data consistently showing that while personal wealth has, on the whole, increased, happiness has decreased. Communities, too, are becoming less integrated and interdependent than they once were. This is not a good outcome for a tribal species.

Is the aim to maximize human potential? No. The concern of our society is not to get as many people as possible to experience the maximum personal growth possible. National funding on mental health is enough to indicate that this is not a serious aim.

Is the aim simply to meet material needs for clean, healthy food, clean water, clean air, shelter and energy for warmth and cooking? The food we eat holds less nutritional value now that we’ve industrialized food production. Furthermore, biocide use contaminates not only the food, but more importantly and more severely the farmers and environment that produced it. There is no clean air unpolluted by man-made chemicals anywhere on Earth. There is no clean, uncontaminated water left, save for what is available in glaciers. Shelter is available, to some at least. Looking at homeless populations, it appears that over-priced shelter is available, provided you are both mentally fit and gainfully employed or with sufficient financial reserves to provide you with a roof over your head. And energy to stay warm and cook food? The same conditions seem to apply as for shelter. So, no, this is not the aim of the current system. If it were a serious concern, it would meet these needs better, assuming we are not all outlandishly incompetent.

Looking at the outcomes, it appears as though the aim of the current system is to accrue and secure financial power to those clever enough, educated enough, lucky enough and/or devious enough to get it and hold on to it. Again, I base this on observation, not ideology. I am not making an argument for or against markets here, I am only looking at outcomes. I know of situations where markets work brilliantly and others where they fail miserably. I am only interested in reality, not ideology, because reality always gets the last punch.

Knowing this, we can ask how well the current system works at delivering our identified human needs. Well, some are met, others are not; and those that are met are almost never done in a sustainable way. Our physical needs are not fully met and to the extent they are, the process of meeting them is eroding our capacity for survival in the long term. Our social needs are not met. The consumption of ever more gadgets is not strengthening families or communities, nor is it cementing real friendships. Too many home buyers are looking to move into a good marketplace as opposed to a good community – one with real bonds between people. Connection to a geological site is not an important factor anymore with many or perhaps most people. Our needs for connection and spiritual and personal growth are not met.

In fact, you can go through the needs in the diagram point by point and find that the current system does a poor job of delivering them and completely overlooks some needs altogether. So there exists a gap between what the system can deliver and what humans need. Filling in this gap is the task of design: identifying the needs and meeting them sustainably in the most efficient way.

Interestingly, the people who are doing this now and living in these designed systems are usually reporting increased happiness as well (happiness that can’t all be solely attributed to Mycobacterium vaccae, the soil bacteria that has been found to boost mood when in contact with human skin). And why wouldn’t they be happy? Their physical needs are getting met. They require less time to acquire food when compared with the need to work for money to then walk or drive to a market to pick out food to then carry home and unpack and load into the refrigerator. They require less energy and money to stay warm or cool in their homes. Their homes are designed around function and not architectural fashion. They are usually folks who are involved with establishing connections in their community. So, many of their intangible human needs are addressed by their systems.

That said, the work we are doing is not reweaving the threads of the tapestry of society. We are just tying up the first lengthwise wrap threads of the tapestry to be woven in the future. We have yet to find all the answers, and the real work is ahead of us. But the choice is sustainability/survival or adherence to a system that we know doesn’t meet our needs. Which path to take seems clear enough.

Filed Under: Article Tagged With: Design

Woody Actinorhizal Plants

Douglas Barnes’s Articles at Permaculture Reflections, Page 6

January 28, 2009 by Douglas Barnes Leave a Comment

  • Read about Rhizobium Symbiosis with Woody Plants here

Dogs don’t eat dogs. At least normal, healthy dogs don’t eat dogs. So, if anyone tells you “It’s a dog-eat-dog world,” smile submissively and slowly back away – you are dealing with a sociopath. The world is, on the whole, a symbiotic dog-help-dog world. Why, even dogs help dogs! Nitrogen-fixing plants are one example of the general pattern of symbiosis.

Plants release an average of 40% of their photosynthates (the products of photosynthesis) out their roots. They don’t do this out of inherent inefficiency. These chemical compounds are doing tasks such as sending signals to call in mycorrhizal fungi and feed those fungi, to share with beneficial nitrogen-fixing and other bacteria, or to make soil nutrients more soluble and available for uptake by the roots.

Among woody nitrogen-fixing plants, there are two varieties: those associating with the bacteria Rhizobia; and those associating with the topic of this article, the actinomycetes Frankia. Actinomycetes are a type of bacteria that grow in long chains of filaments resembling the hyphae, or hair-like roots, of fungi.

Among the woody nitrogen-fixers in temperate regions, actinorhizal plants are an important group. These pioneering plants are able to grow in poor soils, enriching them with nitrogen and organic matter. This makes them very valuable in repairing disturbed or damaged soils.

The diagram below shows the 7 families of woody actinorhizal plants and their 23 genera (I left out the one herbaceous family, the Datiscaceae in the diagram, but it’s in the table).

Actinorhizal families and genera

Plants associated with the actinorhizal bacteria Frankia
Family Genera
   Betulaceae Alnus
Casuarinaceae Allocasuarina
Casuarina
Ceuthostoma
Gymnostoma
Coriariaceae Coriaria
Datiscaceae Datisca cannabina
Datisca glomerata
Elaeagnaceae Elaeagnus
Shepherdia
Hippophae
Myricaceae Comptonia
Myrica
Morella
Rhamnaceae Ceanothus
Colletia
Discaria
Kentrothamnus
Retanilla
Trevoa
Rosaceae Cercocarpus
Cowania
Dryas (some)
Purshia

To rapidly revegetate a damaged landscape, be sure to include plenty of these species to help quickly build up the soils. In areas of very problematic soil, such as arid, tropical and subtropical regions, make 90% of your initial planting of trees nitrogen fixing, pioneer species (associating with either Frankia or Rhizobium), and 10% of species your long-term canopy overstory species. When the system reaches maturity, the proportions will be reversed with 10% nitrogen-fixing, support species and 90% canopy species. The same formula could be followed for temperate regions, but the soils in these area are not so fragile and can stand a lower percentage of nitrogen fixers. A 70/30 or even lower may suffice in these areas, as the seasonal cycles of death and regrowth feed these soils well.

Filed Under: Article Tagged With: soil, trees

Euphorbia tirucalli

Douglas Barnes’s Articles at Permaculture Reflections, Page 6

January 17, 2009 by Douglas Barnes Leave a Comment

Other names that E. tirucalli has gone by include Arthrothamnus tirucalli, Euphorbia media var. Bagshawei, Euphorbia scoparia, Euphorbia media, Euphorbia rhipsaloides, and Euphorbia rhipsalioides.

Euphorbia tirucalli is an African tree that grows in semi-arid, savannah conditions. It is very drought resistant, withstanding long dry seasons. It is salt tolerant and can withstand to just under 5000 ppm arsenic. It will grow from 4 to 15 m tall and at altitudes to 2000 m elevation in hot savannah climates.

It is a coppiceable tree. When coppicing it, cut it at 20 to 30 cm from the ground. It makes good fuel wood with 17,600 kilojoules per kilogram of dry wood; and through pyrolysis, it makes not only charcoal, but also a high octane gasoline substitute. (One to two tonnes of fuel per hectare is what you can expect.) It can also be used as a diesel source.

The timber is useful. And it can be used as a living fence as it is not grazed by animals. Caution must be applied when planting this tree near any human settlement. It must not be in a location where it can contaminate wells or water collection sites as the tree contains co-carcinogens. Latex from the tree can be used as an insecticide and as a fish poison. As an insecticide, it is effective against Colletotrichum capsici, Fusarium pallidoroseum, Botryodiplodia theobromae, Alternaria alternata, Penicillium citrinum, Phomopsis caricae-papayae and Aspergillus niger and against the nematodes Hoplolaimus indicus, Helicotylenchus indicus and Tylenchus filiformis. The latex can also be used as a glue.

It has medicinal properties, though one would use caution obviously. The young twigs from the tree are roasted (presumably breaking down the poisons) and chewed to sooth sore throats. A poultice made from the greenwood is used to treat broken bones. Despite the toxins and co-carcinogens it contains, some of its compounds have been used to treat cancers.

Filed Under: Article Tagged With: Arid climate, trees

The Instant Wadi Well for Arid Climates

Douglas Barnes’s Articles at Permaculture Reflections, Page 6

January 7, 2009 by Douglas Barnes 1 Comment

Rainfall in arid regions occurs in large and infrequent events throughout the year. Because the desert environment is a brittle one and because there is so much rain at one time, tremendous erosion occurs. This leads to the creation of scarps and wadis.

Wadi is simply the Arabic word for a riverbed. In an arid region, its water flow is likely to be ephemeral, particularly in headwaters (where permaculturists are most likely to be working). They are also places where a lot of erosion takes place. Looked at from another perspective, wadis are places where a lot of erosion can be stopped.

After teaching a permaculture course in Jordan, designer Geoff Lawton returned to the area a year later and found that someone had built a gabion (an uncemented rock wall, usually held inside a steel cage) across a particular wadi. Although the 8-foot-high gabion was less than a year old, it was already full of settlement and still had water trickling out of the base, despite the fact that there had not been any recent rains.

This natural tendency for gabions in wadis to quickly fill with water-retaining sediment provides us the opportunity to create what I am dubbing the Instant Wadi-Well (for lack of a better name). After determining where the gabion is to be placed, start with a shallow hole about 2 feet (60 cm) deep in a teardrop shape with the tapered end downstream. Place the first row of stones for the well inside the hole and cement them together, leaving the ground unmortared to allow water to seep in. Keep adding and cementing stones until you reach ground level. Once at ground level, continue up but add an extra 2 layers of mortared stone at the tapering end to allow stability in the face of the rushing torrent and sediment that is to come with the first rainfall. Continue this right up the entire height of the well shaft, making the top row at least 3 feet (90 cm) above the height the gabion will be. After all the sediment moves in, it is likely the well casing will only be 2 feet (60 cm) above the sediment.

All that is left is to build the gabion. Wire cages are not absolutely necessary for the gabion to perform, but they are recommended as they make it far less likely that the rock wall will blow out in the face of the torrent of water, sand and silt.

If the well casing is built strong enough, then there will likely be a well within a few major rain event is. The water will have to be tested as deserts tend to have salty soil. Baring salinity problems, this would be a quick and easy way to establish clean wells and combat erosion at the same time!

This technique compliments other systems as well. For example, if there are storage tanks or cisterns at the top of the scarp, a windmill can be employed to pump water from the Instant Wadi Well to this higher storage. From there, it can be gravity fed down to where it is needed.

Filed Under: Article Tagged With: earthworks

The HA-HA Fence Alternative

Douglas Barnes’s Articles at Permaculture Reflections, Page 6

November 21, 2008 by Douglas Barnes Leave a Comment

In the interests of saving people’s crops from raiding elephants, and to save the elephants themselves, one popular technique, widely taught and promoted in permaculture circles is the “Ha-Ha!” fence. The “fence” is actually a trench about 1.5 to 2 metres deep with steep edges to create a barrier that elephants cannot cross (so people with the fence can watch the elephants and say “Ha-ha!” as their crops are safe). In this way, farmers’ crops can be protected without having to harm or kill elephants.

The drawback to this method, however, is that people have to put in considerable effort to dig these trenches out to protect their crops. Now, thanks to the ingenuity of a Thai villager, adopted by the Elephant Conservation Network (ECN) and the Zoological Society of London, there appears to be a simpler, less energy intensive method to deter elephants. The villager had strung old CDs along his fence in an effort to scare off the elephants. It was observed that, particularly during a full moon, “the CDs twisted and shone, mimicking a person with a torch.” It would be a simple matter to rig up a few throwie-type, battery-powered LED lights so that nights without the full moon would also have protection.

This discovery is promising, but a follow up of the success needs to be seen. Elephants are very intelligent animals and could potentially figure out that the threat is merely a trick. But if it does work over the long term, it means a simple and cheap solution to crop-raiding elephants; and that is good news for people and pachyderms.

Filed Under: Article Tagged With: earthworks

Greywater Guidelines

Douglas Barnes’s Articles at Permaculture Reflections, Page 6

November 18, 2008 by Douglas Barnes 11 Comments

The guidelines in this article are based on Art Ludwig’s industry-leading work. For further information on greywater systems, please refer to Ludwig’s Create an Oasis with Greywater, Branched Drain Greywater Systems, and Builder’s Greywater Guide. These are the best publications available regarding the construction of greywater systems.

Conservation of water is rightfully a growing concern throughout the world. Less than 2.6% of the water on the planet is freshwater. Of that, about 69.6% is locked away in ice and another 30.1% in groundwater, including 13.5% in deep groundwater reserves over 800 metres underground. Only 0.6% of the world’s freshwater is immediately available on the surface via lakes and rivers; and only 0.037% is in the atmosphere at any one time.

Industrial activity and industrial agriculture consume large amounts of the water that is available. And predictions for continental inlands forecast that global warming will bring drier conditions than those that currently exist. Of the total land mass of the Earth, 47.2% is arid, much of that converted to desert by human activity with a further 25% of the land at risk of desertification. And this problem is not limited to poor nations. While 66% of African lands suffer from desertification, 40% of the pastureland in Texas is now too arid for use. And pivot irrigation is turning patches of land on the Great Plains of North America into salted desert in 3 to 4 years. Even former patches of the Amazon rainforest are very close to becoming desert. Global water consumption is rising so fast that by 2025 demand will surpass availability by 56%. We need to shift to sustainable water usage, or we risk creating a planet largely comprised of desert.

One way to use water more efficiently, and return it to the environment clean is by greywater systems. Greywater is waste water from homes from sources excluding toilets. It is water from sinks and drains containing small amounts of nutrient-rich organic matter. Household waste water typically consists of 50 to 80% greywater. To flush this into a sewage system is a waste of life’s most precious resource.

Irrigation by spraying is very inefficient with up to 80% of the water evaporating. This has lead to severe salinisation and desertification in some areas. Greywater drained into mulch or leach pits, on the other hand, has almost no evaporation and results in about 40% of the water being taken up directly by plants (the remainder is filtered by soil microbes before tickling down to recharge groundwater systems).

Advantages

Urban households can save the energy used to purify municipal water by not using tap water for watering plants. Rural households using pumps can reduce their energy and material needs by using greywater over well water for watering.

Utilising greywater also extends the life of septic systems or reduces the load on municipal sewage treatment plants. And in areas where septic tanks are less practical, such as clayey soils and rocky areas where septic fluids cannot trickle into the ground, greywater can help tackle waste water issues.

The use of greywater helps to recharge groundwater.

Good systems are cheap to build. (More expensive systems usually perform poorly.)

Potential Problems

Greywater systems need a certain amount of space. Not every site has enough land for the water generated from the home. Partial sites from only one part (one sink, for example) may be all that can be tapped for a greywater site.

Very wet areas may become saturated with water. Such situations may be impractical or may require a different approach, such as greywater wetlands.

Cold climates make outdoor greywater systems possible through the warm season only.

Reduced water flow from a household can create a problem in urban areas with a municipal sewage system. It may be that the reduction in water flow through the pipes means that there is not enough flow to move toilet solids into the sewage main line.

ValveMany building codes have a lot of catching up to do when it comes to greywater. A system can be built with a diverter to the currently approved (i.e. unsustainable) system. The diverter can then be used to flow water into the greywater system once the code changes. This system can also be used to deal with freezing conditions mentioned above.

Arid regions need carefully managed systems due to their inherent problems with salinity. Proper choice of detergents is important for every system but becomes vital in arid regions. It is a good idea to incorporate rainwater harvesting systems with greywater, particularly laundry greywater. First-flush and/or tank overflow can be connected to greywater drains to wash away excess salts.

Design Considerations

Root cropAn effective, safe greywater system slowly filters water through the soil so that microbes can devour the organic material in the water. The system should be designed such that people never come in contact with the greywater. The systems can be used to assist food production, provided that the plants are not root crops. Don’t spray grey water on plants (or anything else). The water could contaminate the plant and contaminated water droplets could be inhaled.

As a safety precaution, purple pipes are used in the construction of greywater systems, if possible. This colour standard is to avoid any accidental consumption.

Don’t store greywater. It will fester dangerously. Also, design the system to keep water flowing. Systems that allow stagnation will convert relatively clean waste water into a health hazard.

It is a good idea to design the system with a 3-way diverter valve so that greywater can be either directed into the greywater system or to the sewage system. In cold climates, this feature is a necessity.

Make the system so that water sinks into the ground. Don’t allow greywater systems to flow into lakes or rivers, or you risk (illegally) contaminating them. A good rule of thumb is to keep systems at least 50 feet from open water. Local codes may require more than this. (To be fair to greywater systems, it should be noted that about 20% of sewage systems in the U.S. discharge sewage with only solids removed directly into natural open water; and all systems flush into water systems during heavy rains.)

Greywater systems require a change in behaviour. Harsh household chemical cleansers will have to be substituted for greener alternatives.

Consider the bedrock on the site. On a site with limestone, it is theoretically possible, however unlikely, to contaminate groundwater with a grey water system. Greywater systems are still possible, but the potential danger must be addressed in the design.

Avoid perforated pipes for water distribution. First, they clog with sediments from the greywater. Second, even water distribution from the holes is next to impossible. Third, roots will surely clog the system. Dumping directly into a gravel bed system or mulch pit is much better, is simpler to design, cheaper to build, and cheaper and easier to maintain.

Also avoid grease filters and other filtration systems. They will clog and they will clog quickly. If regular cleaning of messy and potentially toxic filters is a necessity of the system, it is likely that the user will stop using the system.

Greywater Volumes by Source

   Washers 115 to 190 litres per day. Good water quality.
Bath tubs 150 litres per use. Good water quality.
Kitchen sink 20 to 60 litres per person per day. Nutrient rich, but high in grease, soap and solids. Use drain screen.
Shower 40 litres per person per day. Good quality. Use drain screen.
Dishwasher 20 to 40 litres per day. Poor quality due to salt in dishwashing detergent.
Bathroom sinks 4 to 20 litres per person per day. Good quality.

Systems

Perhaps the simplest, cheapest, most reliable, best performing greywater system is the branched drain system emptying to mulch pits or leach fields, created by greywater master designer Art Ludwig. In this system, “double-elbow” pipe fittings are used to spread the flow of greywater to different areas of the garden. The branched drain system allows greywater to split into two paths up to 4 times. In other words, 16 drains to mulch pits or leach fields are possible in one branched system. Valves can be placed on each branch to allow that section’s flow to be cut off. The ideal place to do this is on the level section after each double elbow. This will prevent water from backing up and stagnating in the pipes.

Greywater systemThe elbow will effectively halve the flow, but you will need to ensure that the pipe leading up to the elbow has at least 50 cm (about 20”) of straight section. Also, the slope of the pipes should be kept at a fall of 1:48 or steeper to keep the water flowing.

Whether a system is branched or not the ends can be hoses (flexible PVC is advisable as it does not look like a garden hose, thus people are unlikely to drink from it mistakenly), making them movable. This allows different areas to be watered. The advantage here is if one area becomes saturated, it can be shut off.

The “gravity drum” system is ideal for draining washing machines evenly without surges in flow. This system will either have to be branched as above to deliver to a number of sites, or its drainage hose will have to be moved to avoid one location from becoming saturated. Greywater flows from the washing machine’s drainage hose into the top of a 55 gallon plastic drum. At the bottom of the drum, a hole is drilled and a coupling is added to fit a hose to drain the drum as shown. It will be necessary to put a small hole in the top of the barrel, or water will siphon out preventing the machine from refilling (wasting water and making the machine inoperable until the siphon is broken).

Greywater system

Big-brand detergents can be very high in sodium, so it is best to choose a brand that has a low environmental impact. Only in tropical highlands would this extra sodium be beneficial, but only in small amounts. To address the sodium accumulation, it is best to combine the system with rainwater collection from the roof (or other surface as the case may be) to flush out the excess.

Greywater can simply be delivered into a mulch pit by placing the end of the pipe in the mulch. The diagrams below show a slightly more elaborate system that drain into a swale (a water-harvesting ditch on contour).

Greywater system

Leach fields are another simple and safe way to distribute greywater. The diagrams below demonstrate one method to construct a simple leach field. This design delivers simplicity and construction savings at the expense of a somewhat imprecise distribution of greywater.

A trench 1 to 2 meters long and 40 to 50 cm deep is dug and partially filled with gravel or mulch. A hole is cut in the bottom of a clay or plastic flower pot and the greywater hose fitted to it. It is best to push to hose through into the pot and place a coupler on the hose larger in diameter than the hole in the pot. This will prevent the hose from pulling out. Place the pot on the gravel, or if you use mulch, rest the pot on some bricks to keep the pot from sinking into the mulch. Then cover the rest with mulch. The diagram show the tops exposed, but they can be buried in mulch.

Greywater system
Greywater system
Greywater system

Straight greywater cannot be stored for long before it will stagnate and become a smelly health hazard. Once it is treated, however, the water can be held in tanks for later non-potable use. The design below illustrates a simple system using the technique just described to treat water that can be used downstream in the system. The entire unit can be built into a water proofed plywood box or a constructed ferro-cement box.

These leach fields are a convenient solution for cold climates. Outdoor greywater systems need to be shut down in winter as they would freeze up. Leach fields, however, can be incorporated into a greenhouse. Furthermore, any warmth from the use of hot water can be transferred to a greenhouse rather than wasted in the septic or sewage system.

Another option for the treatment of greywater that lends itself well to greenhouses is the constructed wetland. This system is also an option for very wet areas where the ground is too saturated to accept additions of greywater. The water exiting the constructed wetland could be used for irrigation purposes or could go into an aquaculture system. One square foot of wetland surface area will be enough to treat one gallon of water. So, if you produce 50 gallons from one source, you will need 50 square feet of wetland surface area. The fine tuning of these systems can be a bit tricky as nutrient supply determines how many plants can survive. If the system is in a greenhouse, it will be simpler as you do not need to consider the amount of rainfall you can expect to receive. And if the system is too big for the nutrient supply, this can be remedied by controlled additions of actively aerated compost tea.

The diagrams below help to illustrate how a wetland is constructed:

Greywater system
Greywater system
Greywater system
Greywater system

Building Specifics

If your system is to drain outdoors, you will need to check if your soil is capable of handling the load. Dig a 30 cm (12”) deep hole about 10 or 15 cm in diameter. Fill the hole with water 2 or 3 times to saturate the soil. Then place a stake with marks denoting distance (in inches or centimetres) in the hole. Fill the hole with water and time how long it takes for the water to drain down. It will give you the inches or centimetres per minute that the soil is capable of handling.

If you are building a new home, do not mix greywater pipes with blackwater (from the toilet) pipes, including the vents. This makes implementing a greywater system easier. Also, implementation will be easier if you design your greywater pipes to conserve vertical drop as the system will be gravity fed.

Use between 2 inch and 1 ½ inch pipes. Any smaller and clogs are more likely. Any larger and solids might stick on the bottom of the pipe.

Be careful to keep the slope of all the pipes in the system at least 1:48 (1 cm drop over 48 cm, or ¼” drop over one foot) or steeper. And less and you risk clogs forming in the system. Also design the final outlet to empty the water with a fall of several inches. This will prevent solids from backing up at the end of the pipe and clogging.

Map out the system for future maintenance, and be sure to incorporate easily accessible cleanouts.

Filed Under: Article Tagged With: Water

Permaculture in Disaster Areas: Earthquakes

Douglas Barnes’s Articles at Permaculture Reflections, Page 6

June 2, 2008 by Douglas Barnes Leave a Comment

The recent devastating earthquakes in China point to the need for a simple and inexpensive means of dealing with earthquakes. In my region of Canada, earthquakes are few and far between. Yet when I lived in Tokyo, the threat of serious earthquakes was always lingering in the back of my mind – especially after the Kobe earthquake of 1995.

Japan has developed different systems for dealing with earthquakes: shock absorber-like rubber pads to allow the ground to shift under the building, or a ball in an over-sized socket that can slide when an earthquake hits. These systems work fine for those who can afford the significant extra expense they incur for the homeowner. But what of those who cannot afford this high-tech approach? Fortunately, there is a proven, centuries-old technique for building earthquake-resistant structures.

In the Himalayans along the Chinese border, there are stone towers up to 60 metres tall that have been standing for nearly 1000 years.It is amazing for any stone structure, particularly ones so tall, to survive so long – but these ones have done it in a region plagued with earthquakes! The key seems to be a heuristic approach as all of the early models of the towers collapsed in temblors. After repeated tries, success was found by adding triangular ridges running up the middle of each wall. These ridges were able to lend extra support to the walls in the event of an earthquake.

A regular wall like the one pictured is stable when the earth shakes in the direction of the length of the wall. When the earth moves more perpendicular to the wall, however, it is prone to collapse.

Wall

When the wall includes a ridge as pictured below, it becomes more stable when the earth shakes perpendicular to the wall. The ridge feature acts like a tripod leg to give extra strength.

Earthquake resistant wall

Seen from the foundation up, the centre of each wall has a ridge running up its length.

Floor plan of earthquake-resistant structure

With minor adjustments, this feature can be built into the design of a standard home, providing a more earthquake resistance than a regular building would.

Earthquake resistant home

Having allowed huge stone structures to remain standing for a millennium, this method has proven itself to be very effective. By incorporating this feature into new structures, designers can add an excellent level of protection and peace of mind to the inhabitants.

Filed Under: Article Tagged With: Design

Bats

Douglas Barnes’s Articles at Permaculture Reflections, Page 6

May 17, 2008 by Douglas Barnes Leave a Comment

PipistrellusIn North American culture, bats are portrayed as scary creatures. Fortunately for me, I learned at a very young age that bats eat mosquitoes; and since learning this, I have always viewed bats as friends. Most of my permaculture designs call for bat houses, but this element of the design is usually ignored by those implementing the design or is met with strange looks when I suggest the idea. I hope this piece will explain my desire to incorporate bats into designs.

Insect Control

BatAbout 70% of the more than 1,000 species of bats in the world are insectivorous.1 They assist us in controlling biting insects, but their use in insect control is much broader than this.

Recent research from the Smithsonian Tropical Research Institute in Panama shows that bats are vital in controlling plant-eating insects. In control plots with free access for birds and bats, only 4.3% of leaf area was lost to insects. Plots with birds excluded (i.e. relying solely on bats) lost 7.2% of their leaf area. But plots with bats excluded, relying just on birds for insect control, lost 13.3% of their leaf area.2 Furthermore, plots with birds excluded had 65% more insects on the plants compared to the control plot, whereas plots with bats excluded had 153% more insects. Feeding by insects on bat-excluded plots was 209% greater than the control plot, with bird-excluded plots being only 67% greater!3 In other words, in tropical forests at least, bats are more important for insect control than birds. Surely bats play a significant role in insect control in other climates within their range as well. For this reason, I feel they should be a part of permaculture design whenever possible.

Forest Expansion and Maintenance

In the tropics of the Americas, bats can assist in reafforestation. Research by the Leibniz Institute for Zoo and Wildlife Research carried out in Costa Rica found that between 5 and 20 times more seeds are dropped around man-made bat roosting boxes than in areas without the boxes.4 The bats of the Neotropics tend to disperse many seeds of pioneering species, making them potential partners in reafforestation work.

The fruit bats of India tend to maintain forests. They eat the fruits of many canopy species such as guava, thus helping to disperse climax forest species. Unfortunately for the 12 species of India fruit bats, they are all mistakenly classified as pests by the government (though they favour overripe fruit and thus don’t compete with man).5

It is also worth mentioning here that many bats are pollinators, with some plants even evolving flowers suitable to bat pollination.6

Attracting Bats

While some may indeed have bats in their belfry, it is perhaps more useful to build homes for them in locations that are beneficial to your aims. Bats seem to have an easier time locating bat roosts located on poles or on the sides of buildings, and tend to occupy them more readily. They like the interior temperature to be from 26 to 38ºC.7 [See below for links to roost designs.]

Locating bat houses over gardens takes advantage not only of their insectivorous activities, but also of bat guano, a rich source of nitrogen and phosphorus.

A Few Words of Caution

The one drawback of bats is their tendency to be a reservoir species for many viruses (a species that carries a virus without showing signs of infection). They have been found to be carriers of 60 viral species, including lyssaviruses (including rabies), Henipavirus (including Hendra virus, which causes lung haemorrhaging or meningitis, Nipah virus causing neurological and respiratory damage or death), filoviruses (including Ebola and Marburg virus) and possibly the SARS coronavirus. Also, eating bats that have in turn eaten cycad seeds, which contain the neurotoxin β-methylamino L-alanine, can cause serious neurological disease.8

Despite this, there is no need to go running in terror at the site of a bat. Bat roosts can be located accordingly (i.e. not next to homes); and any suspected bat bite should be seen to by a physician. Additionally, their tendency to control the populations of mosquitoes and other biting insects can make them agents of disease reduction rather than vectors of disease.

Useful Bat Links

Bats in Australia http://www.amonline.au/bats/
Some bats of India http://www.batcon.org/batsmag/v13n2-5.html
Bats of Britain http://batsandtrees.com/index.php?option=com_content&task=view&id=13&Itemid=38
Single chamber bat house plans http://www.batcon.org/bhra/economyhouse.html
Attracting Bats http://batcon.org/pdfs/AttractingBats.pdf
Small bat house http://www.dccl.org/information/houses/bat_house_plans.htm
Successful bat houses http://www.batcon.org/pdfs/BatHouseCriteria.pdf

1. http://en.wikipedia.org/wiki/Bats
2. Smithsonian researchers show major role of bats in plant protection
3. Bats Limit Arthropods and Herbivory in a Tropical Forest
4. Fake concrete bat roosts reclaim rainforest; The Bats of India; Effects of Artificial Roosts for Frugivorous Bats on Seed Dispersal in a Neotropical Forest Pasture Mosaic
5. The Bats of India
6. How to Share a Bat
7. Attracting Bats
8. Bats as a continuing source of emerging infections in humans; The reservoir of Marburg virus identified in a species of fruit bat; Scientists detect presence of marburg virus in African fruit bats; Human rabies often caused by undetected, tiny bat bites; Eating bats linked to neurological disease

Filed Under: Article

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