When wet waste is dewatered, it leaves behind a dry biosolid. This byproduct is land filled, burned, used as fertilizer or mixed with compost to produce a viable soil amendment. Yet some states restrict biosolid management and in California strict regulations now limit what water and wastewater utilities can do with biosolids.
One company, EnerTech, invented another option: turning biosolids into clean burning renewable fuels. Through its SlurryCarb process, high temperatures and pressure are used to rupture organic biosolid cells and release moisture. The process turns biosolids into a fuel, similar to lignite coal, with much less energy than conventional drying.
The slurry produced is free of organic pollutants and pathogens and has an energy content of 5,000 Btu/lb. With a shorter drying time - requiring as much as two-thirds less energy than conventional drying - SlurryCarb is about 30 percent cheaper than traditional drying.
This fuel, called E-Fuel, was approved by the California Energy Commission and the Green-e Renewable Electricity Certification Program. To produce E-Fuel, EnerTech needed a full-scale facility, so it teamed with HDR to design and build the first SlurryCarb plant in Rialto, Calif.
The project began with great urgency because several counties in California were passing laws restricting biosolid disposal. Some were completely banning land application or burning.
HDR implemented a fast-track schedule and started designing a processing plant, capable of taking in 675 wet tons per day, with temperature and pressure requirements much different than traditional facilities.
The plant will process sludge from five California municipalities and turns out as much as 145 tons of renewable E-Fuel per day. E-Fuel will replace coal used to power a cement plant, reducing ore consumption and emissions while offering a green, renewable fuel source alternative.
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