Why Waste? 10 Hot waste-to-fuels projects
10. Greenwood Fuels
The Greenwood Energy renewable fuel manufacturing facility in Green Bay, Wisconsin, with an annual production capacity of approximately 150,000 tons, has been in operation since 2009.
“The most cost-effective way to pulp waste paper is using a drum pulper,” said investor Ed Hamrick in a Digest column last year. “A drum pulper is a large rotating drum, usually at least 2.4 m (8 feet) in diameter and at least 20 m (65 feet) long. These are used all over the world to take waste paper.”
The Greenwood solution for separating carbohydrates from MSW is based on this idea. MSW is pulped with process water in a heated drum pulper at high consistency transforming food waste and waste paper to a pulp. Ultimately, it produces three fractions from the MSW. The clean fraction with plastics, metals, glass and other inorganics can be separated using a materials recycling facility (MRF) to get some value from recyclables. The sugar-water fraction and the paper fiber fraction can be used together to produce ethanol or other products using enzymatic hydrolysis. The remainder after enzymatic hydrolysis can be used as a soil improver since there aren’t any heavy metals in the organic fractions.
“Water treatment is an under-appreciated requirement.” said Hamrick. “Garbage is dirty, and any time you pour water over garbage, it gets very dirty. You can’t just flush this water into the sewer. World Waste Technologies built a factory in Anaheim in 2006 to extract paper fibers from MSW. They went out of business and sold the factory for scrap because they were producing dirty water that would have cost more to clean than the money they’d make from the paper fibers. The Greenwood solution uses process water that’s refreshed by the 80% water in the food waste. No fresh water is used, and no waste water is treated. The water from the food waste is eventually disposed of with the residual organics as soil improvement or compost.
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