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We work closely with the investment community to vet and assess a wide range of energy-from-waste projects. We have the front-line experience to assist clients develop and commercialize economically viable energy-from-waste opportunities. We ensure our clients capture the maximum benefits and values.
We have the knowledge base to demystify technologies and separate fact from fiction.
Generating energy-from-waste is not a business to be taken lightly. The conversion process, which consists of a number of complex chemical steps, serves a much needed civic function that at the end of the day should produce carbon-neutral energy in the form of electrons or hydrocarbon fuels.
Processes are new, advanced and in many cases proprietary. Translating patents to operations is far from trivial. The chemistry, thermodynamics and equipment are complex. Efficient process that balance mass and energy are sophisticated and expensive. Demonstration systems may not equate to a viable commercial opportunity.
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Today, organic wastes can be converted into fuel by two different strategies- thermal and non-thermal.
Thermal technologies include gasification, thermal de-polymerization, pyrolysis, and plasma arc gasification.
One technology that is pushing its way towards commercialization combines pyrolysis with high-temperature or low-temperature Fisher-Tropsch (“FT”) synthesis. The Pyrolytic/FT pathway begins with the pretreatment (sorting, crushing, and drying) of the solid waste feedstock, which is then moved to a slow pyrolysis treatment at a high temperature around 900°C. Treatment involves a gasification process in the absence of oxygen) to generate syngas (CO and H2), which is subsequently cleaned and refined into liquid fuel by a FT process. This description is a much simplified version excluding the complexity of the actual process and a number of the process steps, variables and parameters. FT is a sophisticated catalytic technology.
Non-thermal technologies or biological processes used to generate fuels include anaerobic digestion, fermentation production, and mechanical biological treatment.
Anaerobic digestion process utilizes microorganisms to break down biodegradable material in the absence of oxygen, begins with a pretreatment to optimize the amount of digestible material and moisture content as well as to remove harmful contaminants from the organic feedstock, which is then “digestedby bacterial hydrolysis to produce insoluble organic polymers such as carbohydrates.
The carbohydrates are then made available to acidogenic bacteria that convert the sugars and amino acids into carbon dioxide, hydrogen, ammonia, and organic acids. The organic acids are subsequently converted by acetogenic bacteria into acetic acid, along with additional ammonia, hydrogen, and carbon dioxide. Finally, methanogens convert these products to methane (natural gas), carbon dioxide and trace amounts of contaminant gases such as hydrogen sulfide. The methane can be burned to produce both heat and electricity or used as a fuel after “scrubbing to remove the sulfides.”
The one commonality between incineration, FT and biologic conversion of waste-to energy is the use of solid waste as a feedstock. All wastes are not created equally and therefore cannot be uniformly applied to generate energy be it electricity or fuel. This is the primary risk in the energy-from-waste industry. The type and kind of energy generated depends on what actually constitutes the solid waste.
Sorted material with all plastics, glass and metal removed and no construction debris poses fewer issues. If construction debris is included, we may have pressure treated lumber, which has the potential to create some aldehydes in the flue gas such as formaldehyde. There will also be some heavy metals such as cadmium or chromium. Plastics can produce more monoxide, but can also increase tar formation, any of which can inhibit the performance of or poison the FT catalyst. Also the composition of the syngas is critical to the effectiveness and efficiency of the process. In the aforementioned biological process, the feedstock must contain mostly digestible or fermentable material, the right moisture content and must be free of contaminants.
Outlining the right feedstock composition for each of these processes is easier said then done. From the complex and unpredictable nature of solid waste and testing and sampling protocols to determining the syngas or biogas composition from each feedstock and tying that to determine the quality and cost of the product (electricity or fuel), it is far from certain what you get, even under controlled conditions. At the end of the day, the estimated capital cost to build, operate and maintain a waste-to-energy processing plant is highly questionable.