University of Vermont

Green Dorm

Rethinking Waste as a Vermont Energy and Agricultural Resource

by Clean Energy Fund, Guest

Deb KrugWhat role should manure and organic wastes play in Vermont’s Energy Future? The Clean Energy Fund brought me, a Master of Science Candidate in the Department of Community Development and Applied Economics, and a group of three other students to visit the newly operating anaerobic digester at Vermont Technical College in Randolph, VT.  The students in the group were interested in digester policy in the Vermont legislature, renewable energy generation, rural livelihoods, and green technology.  Once in Randolph, we learned how the system has been funded, managed, built, and integrated into the central Vermont Community agricultural and energy sectors.

I am researching policies governing anaerobic digesters for my Master’s thesis, but for folks unfamiliar with the topic: anaerobic digestion describes the process of biological methanogenesis, or the natural decomposition of organic material by bacteria that produce methane or ‘biogas’.  Methane gas is a potent greenhouse gas that is released as manure decomposes, but if produced and captured in an anaerobic digester, it can be repurposed into a valuable fuel to provide clean energy benefits to farms and communities. 

The system at Vermont Technical College is much larger than other Vermont systems, and it currently accepts waste streams from 6 distinct farms. Mary O’Leary, the dedicated project manager and professor at VTC, has submitted permit applications for the digester to accept food residuals including the hops left over from brewing Heady Topper. The VTC students are particularly excited for their campus to smell pleasantly of hops, and have voted to name the digester ‘Big Bertha’ with twitter handle @VTCBigB. Mary O’Leary was pleased to have students involved in many aspects of digester operation and management, from learning the technical skills needed to run the machinery to coordinating the transfer of organic wastes between the farms.  Using organic agricultural and food wastes, the VTC digester will supply energy to the grid through the Vermont SPEED program. The college buys back the energy that they need for the digester and college buildings.       

This digester cost 4.5 million dollars to construct and get on the power grid. Maintenance is also very costly and time consuming; during our visit, trucks were transferring the wastes to a separate storage area. This was because the system had to be completely emptied of the wastes for a repair on the methane bladder.  Mary O’Leary says that the costs are all worth it, though, because digesters also provide tangible benefits in addition to the sale of electricity. The digested solids created by the biodigesters often represent the greatest monetary benefit to the farmers, as they are a substitute bedding substrate for the cows, and farmers can reduce their bedding purchases of other materials such as sand or sawdust.

Vermont’s anaerobic digesters utilize food residuals, manure, and other organic wastes to supply renewable energy.  There are currently 15 digesters in operation, and each one is slightly different in construction and the feedstocks used.  They all rely heavily on renewable energy subsidies and a complex network of relationships between farmers, legislators, state college officials, utility companies, waste and compost haulers and state institutions.  The technology provides a stable source of electricity that does not fluctuate with changes in weather conditions, and so is a renewable complement to wind and solar energy. For centuries, farmers have been using organic wastes to produce energy. 

In my opinion, while our network of digesters is helping to supplant a percentage of fossil fuel power sources while diverting organic wastes from landfills, there are still unanswered questions about the future of the technology in our state.  The future could involve digesters as an integral component of our systems for renewable energy, farm profitability, and organic waste diversion, or perhaps the market has reached capacity given the high cost and unpredictable maintenance needs.  This is why it is valuable for stakeholders in the agricultural and energy sectors to continue to build relationships and share knowledge about anaerobic digesters, and I think that having a community supported digester at our state’s technical college is a great means to start exploring this future.