Turning trash into treasure

Dryers are a crucial piece of equipment in the AD industry, helping operators turn their waste into a lucrative business. Anaerobic digestion is an increasingly popular way to dispose of animal and food wastes. The big advantage is obvious: the ability to generate a gaseous biofuel that can offset natural gas usage. But, many people operating anaerobic digesters inadvertently leave money on the table by failing to understand that the process generates not just one profitable product, but two. The bugs that turn organic material into methane in a digester never close the deal completely, leaving behind a digestate residue full of organic materials the bugs couldn’t process. The digestate contains a good deal of water in addition to those organics. Many facilities treat this material as waste, often sending it to landfills where operators will charge tipping fees of anywhere from $40 (€33) to $70 (€59) per ton, depending on the location. The traditional justification for treating the digestate...