Composting and Renewable Thermal Energy Systems – Case Studies and Trends
Brian Jerose and Gaelan Brown, Agrilab Technologies, LLC, 1662 Pumpkin Village
Road, Enosburg Falls, VT 05450, jerose@together.net and gaelanb@gmail.com; Bruce
Fulford, City Soil and Greenhouse, 285 Cornell St., Boston, MA 02131,
bfulford@citysoil.org.
Composting routinely achieves temperatures of 140 to 160 F during thermophilic
decomposition of biodegradable feedstocks. There has long been interest and attempts
to capture this thermal energy without negatively impacting the biological demands of
the microbiology within the composting mass. There have been incremental gains in
the efficiency and efficacy of compost heat recovery methods over the past 50 years,
with Jean Pain of France, the group www.compostpower.org and the New Alchemy
Institute of Massachusetts demonstrating working examples.
Recent integration of specialized heat exchangers (Isobars®) developed by Joe
Ouellette of Acrolab, Ltd., Windsor, Ontario, with adaptations in feedstock handling and
aeration strategies has resulted in significant performance gains. Since 2006 four sites
in VT, NY and NH have implemented composting and thermal energy systems using
this Isobar® heat exchange technology. The most recent installation by Agrilab
Technologies LLC is at the University of New Hampshire, Organic Research Dairy
Farm. Further gains in efficiency are being demonstrated and tested through using odor
biofiltration and air-to-air exchange as secondary heat recovery, lead by Bruce Fulford
of City Soil and Greenhouse in Boston, MA.
One operating composting and thermal energy system site example is saving
$30K annually in fuel oil, labor and equipment costs, while generating increased
compost sales revenues. Average thermal energy output is 200,000 Btu/hour at
average temperatures of 110F to 120F, with peak temperature observed of 146F.
Furthermore, adoption of negative aeration systems provide substantial improvements
in efficiency of compost production, with less energy required for producing each ton of
compost.
This presentation will describe case studies for the implemented sites and trends
in this growing practice of integrating composting and thermal energy systems in order
to heat greenhouses, buildings and meet other hot water demands. Methods to
evaluate the suitability of compost heat capture at existing and planned composting
sites will be discussed.
Submitted June 30, 2013