Current State of the Art


Since reading in the early 1990s of ecologist C.S. Hollings efforts, I have been taken with the comprehensiveness of his diagram and its similarities to OARS’ logo.

I’m suggesting biological repair rather than a technological fix; managing the semi-cycle of return through dragon husbandry — for sustainability

In many situations, digesters may be most usefully understood as livestock — as intestine extensions rather than technological units. Most digesters are very similar to bovine beasts. They don’t need to be fenced in – though others may need fencing out. They do need to be fed and watered appropriately — and not poisoned. They even like agitation, or, with rubber/plastic systems, deep massage.

I continue to see much of the high-powered, high-tech approach to digestion as an attempt to enslave the beasts for an overly centralized, unsustainable system. Rather, I suggest a smaller-scale, symbiotic inter-relationship with digester raisers getting a fair share for rent and care and then letting them be. I’d minimize masonry and recommend longer, intestine-like beasts enclosed in supple bodies made out of rubber and/or plastic (Taiwan’s Red Mud, EPDM) These can most simply lie in a well-smoothed, shallow trench — but protection must be considered.

Decisions on investment in a digester are quite similar to decisions about investing in any other livestock. Again, digesters can be fed almost anything organic that is not mostly lignin. They do need enough water to keep them anaerobic. One needs to manage their tail-end products: solids, liquids and gas. Handling the biogas needs some care but eases cooking and reduces air pollution. The solid and liquid resource residue will probably not be perfectly sanitized, but 30 days in a digester does destroy all of most, nearly all of many more, and the majority of the most recalcitrant pathogen vectors that may be left. Odors are greatly reduced and transformed and fly growth is not supported. Digestion certainly results in NO NEW pathogens that are not fed into it – and anaerobes cannot survive with exposure to oxygen. The soil-building and fertilizing solids can be scuffed into the top of the soil. The higher nutrient liquid can be spread under crops rather than onto leaves, but with no fear of “burning” the plants.

Perhaps the primary differences between decisions about raising other livestock and raising dragons result from the accompanying increased awareness of the biological energy and material values of residual organic resources. At smaller scales, digesters almost beg to be symbiotically integrated with other cyclical and productive biological activity — diverse livestock, greenhouses, expanded or more intensive gardens, hydroponics, aquatic plant and animal channels and ponds, etcetera. Of course, such considerations are appropriate at all scales, but they are crucial to viability for smaller systems.

As to costs, I prefer the question, “How much will it cost NOT to take advantage of possibilities offered through anaerobic digestion.” And to this I answer:

  • It will cost the nutrients volatilized and leached from compost piles which would be kept available for re-growth through digestion;
  • Unless means is found for utilizing the heat from composting, it will cost the solar energy component of organic residues which is made available in the biogas from digestion;
  • In situations where the biogas would replace biomass fuels (like dried dung) it will cost the combustion of all that biomass which could have been left growing or used in other ways;
  • In situations where the biogas would replace biomass fuels or coal briquets, it will cost the increase in respiratory health which would have occurred with digestion;
  • In situations where the biogas would replace a commercial fuel, it will cost the price of the commercial fuel;
  • In situations with little or no sanitation facilities, it will cost the decrease in enteric disease infection which would have occurred with digestion; and
  • Since all of this is done at a local level through intensive management of the semi-cycle of return, it will cost all of the energy, etcetera, inputs which would be made unnecessary by digestion.

Should a reasonable carbon tax ever be instituted, this final point would likely be overwhelming. I dealt with all of this in more depth in the “Bioeconomics” chapter of my Final Report .

I suggest that dragon husbandry offers a sustainable means for management of the semi-cycle of return so as to develop an increasing spiral of biomass and diversity. I welcome any discussions and communications through email or the blog link.

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