|Enerkem’s four-step process uses gasification and catalytic synthesis to convert waste to liquid fuels. Click to enlarge.|
The city of Edmonton, Alberta, Canada, has signed a 25-year agreement with GreenField Ethanol, Canada’s largest ethanol producer and Enerkem, the developer of a thermochemical (gasification and catalytic synthesis) process to produce synthetic fuels, for a facility to produce biofuels from municipal solid waste (MSW).
The C$70 million facility will initially produce 36 million liters (9.5 million gallons US) of ethanol per year, according to the partners. As part of the agreement, the City of Edmonton will supply a minimum of 100,000 tonnes of sorted municipal solid waste per year.
|Site of Enerkem/GreenField Ethanol future plant in Edmonton (indicated in orange on this layout). Click to enlarge.|
Greenfield Ethanol and Enerkem will be jointly responsible for financing the project and for constructing, owning, and operating the plant which will be located at the Edmonton Waste Management Centre in Edmonton, Alberta.
The City of Edmonton and the Government of Alberta through the Alberta Energy Research Institute (AERI) are contributing $20 million to the facility. The City of Edmonton will also contribute $50 million to a related processing facility and research facility. AERI’s total contribution to all the components is $29 million.
This plant is the first to be announced by Greenfield Ethanol and Enerkem since their announcement earlier this year of their partnership to jointly design, build and operate commercial next-generation ethanol plants.
Enerkem also is building a smaller industrial-scale demonstration plant in Westbury, Québec, which is due to be operational in the fall of 2008. The plant will produce up to 5 million liters (1.3 million gallons) of cellulosic ethanol from creosoted electricity poles and other waste materials.
Enerkem has been operating a pilot plant since 2003. This pilot plant has logged more than 3,000 hours of operation, using more than 20 types of feedstock, ranging from sorted municipal solid waste to wood chips, to produce methanol and second-generation ethanol.
Enerkem uses a four-step thermochemical process for the conversion of waste to fuels:
Feedstock pre-treatment. The feedstock is dried, sorted, and shredded, and then stored in a container that is connected to the gasifier via a front-end feeding system.
Gasification. Enerkem uses a bubbling fluidized bed reactor with a front-end feeding system that is capable of handling fluffy material with no need to pelletize it. Slurries or liquids can also be fed into the gasifier through appropriately designed injectors. The gasification is carried out using air as a partial oxidation agent or using oxygen-enriched air, with the oxygen-enrichment level tailored to the desired composition of the synthetic gas. The presence of steam at a specific partial pressure is also part of the process.
The gasifier operates at low severities (temperatures of approximately 700º C and pressures below 10 atm), which allows for the use of known, available, and inexpensive construction materials and refractories.
Cleaning and conditioning. The resulting syngas is cleaned and conditioned for use with existing and known catalysts. This is accomplished through a sequential conditioning system, which includes cyclonic removal of inerts, secondary carbon/tar conversion, heat recovery units, and reinjection of tar/fines into the reactor. The gas that is produced by this process is ready for conversion into liquid fuel.
Conversion into liquid fuel. Using a sequential catalytic conversion process, the syngas is finally converted into high-value, market-ready fuels and chemicals. Products such as methanol can be sold directly or used as intermediate products in the creation of other products, such as ethanol, synthetic diesel, dimethyl ether, and synthetic gasoline.
Enerkem says that up to the production of the syngas, its technology uses only around 10% of the energy produced for its internal process needs. The company says that it can produce approximately right times more net energy than a high-temperature technology such as plasma gasification.
|The Enerkem process supports a variety of product pathways. Click to enlarge.|
The integration of bubbling fluidized bed technology and advanced gas conditioning, allows for the use of a wide array of feedstocks while achieving a synthetic gas as clean as natural gas and ready for subsequent processing into synthetic fuels. Catalytic synthesis can produce second-generation ethanol; ogliomerization can produce synthetic gasoline; DME synthesis can produce DME, and Fischer-Tropsch catalysis can produce synthetic diesel.
Enerkem says that its process can convert 1 tonne of waste into up to 360 liters (95 gallons US) of ethanol; 100 liters (26 gallons) of potable water; and 150 kg (330 lbs) of char and gasifier inerts.
There are also a number of other MSW to biofuels development projects underway, using different production pathways. Coskata, for example (one of the higher profile ventures because of the investment from GM), uses a combined thermo-biochemical process: it gasifies waste, including, theoretically, MSW, but then ferments the resulting syngas to fuel. (Earlier post.)
Blue Fire Ethanol, which uses a concentrated acid hydrolysis technology to pretreat the MSW, will receive up to $40 million from the Department of Energy (DOE) for a plant in Southern California sited on an existing landfill that will produce about 19 million gallons of ethanol a year. As feedstock, the plant would use 700 tons per day of sorted green waste and wood waste from landfills. (Earlier post.)