Food Waste and “Industrial” Composting James Dontje Director Johnson Center for Environmental Innovation Environmental Studies Program Gustavus Adolphus College 25 March 2015

Prerequisites for successful cafeteria scale food waste composting Supporting cast Community (student!) support Material handling and source separation

Supporting cast Physical Plant Director supportive – “self-hauling” operation – experience composting landscape waste Dining Services Director supportive – “wholly owned” – history of environmental discussions (Kitchen Cabinet) Environmental Studies faculty supportive – ready to commit when funds became available

Supportive community 2011 Student Senate resolution urging composting Student activism on this issue Student garden, Big Hill Farm, highlighted opportunities for nutrient recycling

Material handling and source separation Key to successful organics composting “A la carte” dining service model reduces waste Food waste pulping system works with compost collection Waste hauling equipment already part of physical plant operations

Composting technology In-vessel vs. static or mix pile Labor and emissions management (regulation?) Winter weather Reviewed a range of in-vessel options – Completely contained = expensive – Drum systems = maintenance and repair – Balance of cost and complexity Reserve capacity

Green Mountain Technologies Earth Flow Unit 24 foot long Aeration from underneath Automated traveling auger Head space ventilation 1000 lbs/day capacity

Other design/operating parameters Leaves as carbon source (supplemented by paper) Little need for additional water Aeration need variable (currently 50%) Biofilter for odor reduction Recipe calculation from mpost-calculator-tool/ mpost-calculator-tool/ ~21 days in vessel; 1 month curing

Operating experience: Trouble-free start up (1-week to full composting) Able to maintain “Processing for Further Pathogen Reduction (PFPR)” temperatures (<130F) through “polar vortex” Odors in vicinity but manageable Probably not always enough carbon Achieving compost maturity in vessel Low levels of contamination

Mechanical issues: Condensate frozen in aeration line (installation issue) Position sensor failure (one design and installation related, the other?) Auger motor failure (moisture but also installation damage?) Door latches

Compost use: Student garden Landscaping Community garden

Education and research Sustainable systems model Student projects and garden Compost maturity and nutrient measurements Heat capture