One Firm’s Quest to Develop a Portable Organics Digester

Usually when referring to the use of farm animals to create bioenergy, you are discussing waste-to-energy options and resources. But one Seattle, Wash., company is trying to change that.

Impact Bioenergy has created the HORSE system for generating bioenergy. HORSE stands for a high-solids, organic-waste, recycling system with electrical-output. It is a portable digester.

“Impact Bioenergy prefabricated modular systems can process 25 to 925 tons per year of waste materials,” says Jan Allen, president, Impact Bioenergy. “Renewable energy can be in the form of building heat, hot water, radiant heat, light, electricity and prime motion. Fertilizer can be in the form of liquid fertilizer, dried fertilizer, fertilizer pellets and compost.”

The system was introduced to the U.S. in February. The first North American system was delivered to British Columbia. Allen says Impact is crowd-funding to put one or two HORSES on the ground in Seattle area as reference plants.

“Our crowd sourcing goal is to both connect like-minded people and to raise enough money to build a containerized version of the HORSE. Individuals and organizations can make an impact and be part of this. We have a specific project in Seattle and are hoping to build more as a demonstration to allow early adopters and innovators a chance to operate this system,” he says. “The vision is to become more self-sufficient and to make renewable energy on your property and fertilize your own or a nearby garden or farm to grow food and flowers.”

Allen says the HORSE system is both a sustainability and society game changer.

“It’s all about the quadruple bottom line: people, planet, profit and progress. There are 700,000 restaurants and 4,000 college campuses in North America,” he says. “Each one should have their own HORSE. Just imagine the sustainable energy revolution for islands, resorts, zoos, museums, schools, parks, convention centers, farmer's markets, music venues, apartments and corporate and municipal campuses as they turn food scraps into energy.”

The HORSE system can take a wide range of organic wastes including kitchen trim, plate scrapings, meat, grease, oil, all edible liquids, seafood, dairy products, starch, sugar, fruit, vegetable, small bones, soiled paper products, napkins, tissue, paper towels, waxed paper, grass clippings, leaves, fats, fryer oil, grease trap waste, beverages, alcohol, soup, condiments, manure, human waste and food processing wastes. 

Because it is a liquid system, all organic materials need to be reduced to one-inch or smaller pieces. Organic wastes are blended and homogenized for three to four days and metered into the digester. The digester is a closed system (sealed from the atmosphere), mixed and heated to about 100 degrees.

This produces biogas that can be used as renewable natural gas. The biogas is stored overnight within the system and can be used during peak energy demand periods during the day. The HORSE system creates renewable energy in the form of hot air, hot water, radiant heat, electricity or cooking gas.

Allen says that liquid organic plant food in the form of nutrient-rich water is produced daily in equal volumes to what is put into the system. There are only two moving parts in the digester—mixer and heating pump—and this liquid is produced by gravity flow as new food waste is metered into the system.

“Energy is produced by microbial conversion of the calories in the organic waste by fermentation. This is biomimicry as we have designed a living machine that functions like a HORSE or other animal with a digestive tract,” Allen says. “It can create up to 37 megawatt hours of raw energy at full operating capacity. As renewable gas that’s 125 million BTU per year—4.3 megawatt hours of this energy is electrical output.”

The HORSE system also can create 5,400 gallons per year of liquid fertilizer, according to Allen.

“This is the first time a manufacturer has commercialized anaerobic digestion at this scale, enabling customers to generate energy from food waste and other organic materials,” he says. “This creates the opportunity to eliminate the costs and environmental impacts associated with the disposal and hauling of organic, carbon-based wastes to distant landfills by converting them into heat, electricity, vehicle fuel, and soil amendments on-site at their point of generation.”

Allen says one of the benefits of the HORSE system includes eliminating garbage pickup and the carbon emissions associated with long distance trucking.

“Imagine a technology that can divert waste and create energy off-grid. Imagine eliminating the organic waste from the disposal system. Imagine making it into two valuable new resources for commercial use,” he says.