Technology
Overview
The Edmonton Waste-to-Biofuels project integrates both the City of Edmonton’s sorting and processing methodology as well as Enerkem’s thermo-chemical technology platform.
Sorting phase: Leading-Edge Integrated Waste Processing and Transfer Facility
This facility has three distinct operations, including a waste transfer operation, a pre-processing operation and a refuse derived fuel plant. The facility will ensure that the waste is sorted, prepared and then transferred to the appropriate downstream plants like composting and biofuels plants.
In the pre-processing operation, residential and suitable commercial waste is sorted mechanically and manually into three streams:
- organic materials which are conveyed to the Edmonton Composting Facility;
- cardboard, metals and plastics for recycling;
- and non-recyclable, non-compostable waste for conversion into refuse derived fuel (RDF).
In the refuse-derived fuel plant, a mechanical system will prepare and shred feedstock for the Biofuels Facility. Non-recyclable and non-compostable waste is converted into RDF, which will in turn be converted to methanol and ethanol at the planned Biofuels Facility.
Converting phase: Commercial
Waste-to-Biofuels Production Facility
The biofuels production facility uses Enerkem’s thermo-chemical process. Enerkem’s innovative technology is the result of several years of research and over 3,600 hours of piloting. The technology is also currently in operation at Enerkem's commercial demonstration facility in Westbury, Quebec.
A Step-by-Step Guide to Enerkem’s Technology Platform
The process involves heat, pressure, advanced chemistry and the use of cutting-edge catalysts. It has a positive energy balance, since gasification requires less energy than it produces. It also requires minimal use of water, and can even be a net producer of water. The process can be broken down into four steps.
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Step 1- Feedstock pre-treatment
The sorted MSW is shredded and then stored in a container that is connected to the gasifier via a front-end feeding system.
Step 2- Gasification
The gasification process converts carbon-rich residues into a uniform synthetic gas (syngas). The heat and the pressure break apart the chemical bonds of the waste material into a syngas. The conversion of waste materials into syngas takes less than 10 seconds.
Step 3- Cleaning and conditioning of the synthetic gas
The syngas is cleaned and conditioned in order to prepare it for catalytic conversion to methanol and ethanol. The cleaning process is accomplished through a sequential conditioning system, which includes cyclonic removal of inert matter, secondary carbon/tar conversion, heat recovery units, and reinjection of tar/fines into the reactor. The syngas that is produced by this process is ready for conversion into liquid fuel.
Step 4- Conversion into liquid fuel
Using a sequential catalytic conversion process, and commercially available catalysts, the syngas is converted to high-value, market ready fuels and chemicals. The catalysts rearrange the molecules in the gas into methanol and ethanol.
Second-Generation Biofuels
Second-generation biofuels are produced from a large base of biomass materials, such as forest and agricultural residues as well as municipal solid waste. They differ from the first-generation of biofuels (often called agrofuels) in that they are not produced from crops such as corn, sugar cane, and wheat. Second-generation fuel-production technologies can generally be divided into two types: enzymatic (or biological) technologies and thermo-chemical technologies.
Thermo-chemical technologies, such as Enerkem's, use heat to convert carbon-rich materials into a synthetic gas. This syngas is then purified so it can be transformed into alcohols such as methanol and ethanol. It is also possible to produce other fuels, such as synthetic diesel, synthetic gasoline and dimethyl ether as well as chemical products.
Enzymatic technologies seek to recover and ferment sugars that are found in lignocellulosic (tree and plant) materials. These technologies aim at recovering the sugars using engineered enzymes to break down the tree and plant material, after which it is possible to hydrolyze the cellulose into glucose, from which ethanol is easily made.
In a recent joint publication released by the Sierra Club and Worldwatch Institute, entitled Smart Choices for Biofuels, thermo-chemical technologies are highlighted as having “a potential advantage over biochemical technologies as they can convert almost any kind of biomass into fuel”.
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