in Vermont, we are seeing our own manifestations where river mouths meet Lake Champlain. Watersheds that encompass large numbers of dairy farms shed nutrients into the lake, leading to the despoilment of shorelines, fisheries and wildlife habitat. This is typical of the situation across the US, where agricultural nutrients cause over 50% of the pollution of our freshwater bodies. The National Science Foundation recently reported that nutrient pollution has now been identified as the aggravating factor in the macabre deformations seen in frogs across North America.

These problems are seen worldwide from the watersheds of the Danube to the coral reefs of the Indo-Pacific. The problem is only compounded by the often desperate circumstances of the world’s farming communities, where low farm incomes exacerbate the overuse of fertilizers and destruction of natural buffers.

The impact on water quality is matched by the atmospheric impact of incomplete manure and nutrient management. As farmers store their manure while waiting for the opportunity to spread it on their fields, volatile compounds are steadily lost. Methane is foremost, followed by ammonia, followed by nitrous oxide – all significant greenhouse gases. Even our “best management practices” encourage farmers to store manure in open pits for up to six months, leading to substantial atmospheric losses of greenhouse gases.

The irony of this situation is that farmers pay for the nutrients and other compounds that are lost from their fields and they should have an economic incentive to reclaim them.

The Solution: manure digesters and biological trickling filters for small farms.

Consider that the farm is itself an ecosystem through which nutrients cycle as the fields are planted, fertilized and harvested. Animals are fed from the harvest and while animal products are exported from the farm, their manure accumulates until it is once again spread on the fields. By adding steps to this cycle to extract further value from the manure, we aim to produce fuels, treated fiber and stabilized nutrients that can be used on the farm and that will create cost offsets that make these changes economically attractive to the farmer. These extra steps are automated for the already busy farmer and the equipment can be added alongside existing farm structures. My hope is that Bucky would approve of our efforts to attract great numbers of farmers to make incremental changes to their small farms in order to make substantial improvements to agriculture’s overall environmental footprint. My Vermont-based research and development team has spent the past five years (three working for Avatar) to create an anaerobic digester and effluent system for the small dairy farm. This would be one of the first digesters in the U.S. built to service a dairy farm with a herd size of only 50-100 head. It would also be one of the first systems to further treat the digester effluent in order to stabilize and separate nutrients for reuse. The system is designed to address two specific challenges to farm viability: improved manure and nutrient handling and the reduction of farm energy costs.

Our federal and state agencies typically address these issues - nutrient management and on-farm energy generation - separately, contributing to the perception that digesters are not feasible on small farms. It is not until the farm operation is viewed through the lens of human ecology that the benefit of treating them simultaneously becomes obvious:
* The use of the digester’s biogas to generate energy makes it practical to implement further nutrient management measures.
* By sending the manure directly into an anaerobic digester then into aerobic biofilters there is minimal opportunity for atmospheric emissions.
* Anaerobic digestion destroys the noxious odor of manure, improving the farm’s relations with its neighbors.
* The digestion process destroys the odors and kills a high percentage of pathogens in the manure, allowing the solids recovered by separation to be used for bedding material in place of increasingly expensive sawdust or sand.
* The digester actually converts available nitrogen to ammonia. Treating the separated liquids through the aerobic trickling filters converts this to non-volatile nitrate
* As the liquids circulate in the trickling filters, phosphorus-laden particulates settle out, allowing the farmer to control application of phosphorus to fields.
* Treated liquids can be sprayed over crops during the growing season to apply nitrogen at a rate that matches plant uptake.

By managing the economics and ecology of small dairy farms simultaneously the farmer realizes a greater set of benefits.

System Overview:
While anaerobic digesters are not capable of directly reducing the levels of nitrogen or phosphorus in manure (the levels of ammonia may actually increase in the effluent), Avatar’s effluent treatment system provides additional opportunity for nutrient management.

Step 1) Manure is pumped into a pre-heating tank, where the temperature is raised to 105ºF. Manure is injected into the digester hulls. Each hull is sized to accept the manure from 40 to 100 cattle. External heating coils maintain the hull’s temperature to promote digestion during the 20 day retention time.
Step 2) Manure is pushed into a holding tank that feeds the separator. A solid and liquid fraction are produced from the digested manure.
Step 3) Finally, the liquid fraction flows to a series of trickling filters and settling tanks. Liquids are pumped over tubular nets containing filter media that support growth of aerobic bacteria. The actions of these bacteria reduce the viscosity of the liquid and allow larger particles to settle out with the phosphorus. Bacteria also convert ammonia/ammonium into nitrate.

Features of the Avatar Digester The Avatar hybrid plug-flow digester was designed with the reality of farm life and high-throughput production and installation in mind:
* Economy of scale is achieved through a large market, pre-engineering and pre-fabrication.
* Digester hulls are modular, using short pipe sections (8’ wide x 8’ long) to simplify installation without the need for custom engineering and/or major construction.
* Clean-out of the digester hulls is simplified, taking only a few days rather than the months required to clean large-scale digesters.
* Elevated tail sections passively pressurize the gas within the digester allowing biogas to be piped, filtered and used in boilers or gensets without the need for compressors.
* Internal baffles permit the stable growth and continuous inoculation of organisms.
* Construction using tubular sections allows the digester to be disassembled for relocation or reconfiguration. Use of moveable components and minimal concrete means that the Avatar digester is a ‘moveable asset’ and more easily financed.
* The pre-heating tank can act as a mixing tank for the addition of non-manure feedstocks, such as food processing wastes.

Financing and Implementation
Grant funding has been tremendously important in allowing my work to reach the point of attracting private investors. Even with private funding, grants continue to be an important means of supporting our experimental R&D work. In 2005 Avatar was awarded a grant through the Vermont Alternative Manure Management Program. Avatar provides matching funds to these grants for salaries and other project expenses. As our pilot system nears completion, Avatar is already preparing to begin installing demonstration units on other farms in Spring 2008 and move into full-scale production by late 2009. My team has already prepared a draft installation manual for these demonstration sites. My R&D group will operate the pilot system for five years, studying its nutrient and energy output and using it as a test bed for innovation. The demonstration units will provide our team with the opportunity to learn how to efficiently install new systems.

We are currently negotiating strategic partnerships with farm equipment suppliers and fiberglass manufacturers in order to streamline the production and installation of our units. We have already built relations with fabricators and equipment installers in the Northeast and Northcentral and Midwestern dairy regions, in our hopes to keep shipping and construction costs to a minimum.

Finally, several lending agencies have agreed to make loans to farmers that allow the farmer to pay off the system at a rate comparable to their monthly electric bill. Avatar will work with farmers to obtain funds from state and federal granting programs.

Avatar’s investor group also serves in roles of marketing, book-keeping, and technical advisors. Avatar will hire additional personnel to staff installation teams and to provide office support as demand increases. Eventually, we anticipate building regional installation and service teams. Research and development is expected to continue under my direction in our Vermont office, though engineering will continue to be outsourced.