Anaerobic Digestion

Harvest’s Energy Garden in Richmond, BC. Photo from December 2012

A Superpowered^™ Approach To Managing Organic Waste

Anaerobic digestion uses naturally occurring microorganisms to break down organic materials and produce biogas, a mixture of methane and carbon dioxide. The biogas can be combusted to produce renewable electricity, cleaned to pipeline natural gas standards, or further processed into compressed natural gas (CNG) fuel. Through anaerobic digestion, many goals can be accomplished:

Divert organic materials from landfills and incinerators
Generate clean, distributed, renewable energy
Restore and maintain healthy soils using compost products
Displace chemical fertilizers
Create green jobs

We design, build, own and operate a platform of Superpowered^™ anaerobic digestion systems to meet the needs of each site. The most common differentiation is the “solids content” of the material being processed:

Harvest’s Energy Garden in Central Florida uses low solids anaerobic digestion to turn biosolids and food waste into clean energy and natural fertilizers. Photo from Oct 2013.

Low solids anaerobic digestion – best for pumpable slurries like manure, wastewater and pulped food scraps that are less than 20% solids content. Materials are blended, mixed with heated water and innoculum to kick-start the digestion process and pumped into the chamber(s) where digestion and biogas production occur. After digestion the solids are separated from the liquids and either composted or pelletized for land application. The liquids are processed through a wastewater treatment system. Many low solids anaerobic digestion facilities are successfully operating around the world, commonly at municipal wastewater treatment plants and dairy farms.

High solids anaerobic digestion – also known as “dry fermentation”, best for stackable materials like food scraps and yard debris that have a solids content of 25% – 50%. Materials are mixed and loaded into digestion chambers using a wheel loader. After two weeks in the digestion system the partially degraded material is aerobically composted.