Wednesday, June 25, 2008

Combined Heat and Power for Food Plants

Many types of food processing plants including sugar and starch refiners, breweries, cereal makers, potato processing plants, etc. can use the organic waste byproducts of their normal operations to create fuel that will both provide process heat and generate electricity for plant operation--CHP. If they are truly thrifty, they can then mine the waste heat from processing to generate yet more electricity, and sell it to the utility if it exceeds their needs.
The Royal Brewery CHP plant will produce 7.4 megawatts (MW) of thermal power and 3.1 MW of electricity, fueled by a mixture of spent grain left over from the brewing process and clean wood waste. Wood is required due to insufficient quantities of spent grain.

Before the spent grain is fed to the boiler, the moisture content is reduced from 80 percent to 60 percent, Kuitunen explains. “That is good enough for our combustion system.”

Food processing giant Tate & Lyle PLC is installing a biomass-fired CHP system at its east London sugar refinery. Wheat husks, a byproduct of flour production, will fuel a $41.4 million, 65-MW biomass boiler. Using biomass will slash energy consumption from fossil fuels by 70 percent, with a corresponding 70 percent reduction in carbon emissions. Steam produced by the boiler will generate electricity and satisfy the refinery’s process heat requirements. Excess power produced by the system will be sold to the National Grid.

McCain Foods in Whittlesey, U.K., constructed an 828,000-square-foot covered anaerobic lagoon to process wastewater from the U.K.’s largest french fry factory. Wastewater containing potato starch generated during processing is piped to the lagoon and produces more than 400-standard-cubic-feet per minute of biogas. The firm may add other potato wastes, such as peels and nubbins, to increase biogas production.

Initially, the biogas fueled a boiler to produce steam but an engineering study determined that more value could be derived from the biogas by producing electricity, explains Carmine Fontana, vice president of gas processing for Ontario, Canada-based Eco-Tec. The biogas now feeds a General Electric Jenbacher reciprocating engine that produces more than 1 MW of electricity, satisfying 10 percent of the plant’s electrical requirements. Heat generated by the engine warms the lagoon.

Austria-based Agrana, one of Central Europe’s leading sugar and starch producers, recently installed a $10.5 million AD system at its sugar refinery in Kaposvár, Hungary. The digester processes spent beet pulp and beet syrup to produce almost 3.9 million cubic feet of biogas a day.

The biogas feeds the plant’s boiler to produce steam, which drives a turbine generating electricity and is used for process heat. The biogas replaces 60 percent of the plant’s energy requirements and cuts carbon emissions by 10,000 tons.

Insource is focusing on six sectors in the food and drink industry that are well-suited for waste-to-energy systems: distilling, brewing and soft drinks, red meat, dairy products, fruit and vegetables, frozen and chilled foods. “We are looking for high volumes of consistent types of wastes, which work best with the technologies available,” Coate says.

The company is currently working with five major U.K. food and beverage companies. “In many cases, AD and CHP are the most appropriate technologies,” Coate says. However, the company can deploy a wide range of technologies since no single technology can treat all wastes.

Recently NISP started working with Severn Trent Water, the U.K.’s largest independent water company, to divert industrial food waste from landfills to STW’s AD plants across the U.K. “There is a big move in the U.K. for companies to build new AD plants to process food wastes,” says James Woodcock, NSIP practitioner. “Being familiar with STW and the water industry in general, I thought there are a lot of these plants in existence already treating sewage mixed with industrial waste.”

STW utilizes AD to treat more than 700,000 gallons of wastewater and sewage a day. Biogas produced by the digesters fuels CHP units generating 154,000 MW hours of electricity, representing 17 percent of STW’s electrical requirements. Thermal energy is used in the treatment process.

Adding industrial organic wastes to STW’s AD systems will increase biogas production and renewable energy generation, improving the sustainability of the treatment process. Industrial food waste producers will benefit by cutting waste disposal costs by as much as two-thirds over landfill costs, Woodcock says. __BiomassMag
Most large plants have the ability to either cogenerate heat and power, or the ability to mine significant amounts of waste heat to create electrical power. Being able to use waste products as fuel to power the CHP is an added dividend.

Ethanol biofuels makers have been learning critical lessons about resourcefulness in the face of rising fuel costs. The ones who succeed will be the ones who take advantage of every source of energy they can find--particularly energy that once was considered "waste."

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Blogger scottkuhlke said...

@ McCain Foods in Whittlesey, U.K, what part of the engine heat is used to warm the lagoon? Is it the heat to cool the engine? If so, what temperature does the heat come out at? If you know, please advise, thanks!

4:53 AM  
Blogger al fin said...

I'm not sure, Scott. Anaerobic fermentation produces heat itself, and since the lagoon is covered it could probably be insulated to retain more heat, and reduce heat draw from the reciprocating engine waste heat.

Assuming McCain's lagoon functions at thermophilic temperatures (just above 50 C, or 130 F), the heat needs could be significant unless the lagoon is well insulated.

8:17 AM  

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