Technology

Powers Energy facilities use proven gasification and syngas conversion processes along with conventional materials handling and ethanol distillation techniques to produce fuel-grade ethanol, electricity, and recyclable metals and glass commodities.  We call the ethanol from our facilities "bioethanol" because it is made mostly from biogenic materials, which are materials produced by biological processes of living organisms.  Biogenic generally refers only to organic non-fossil material of biological origin.  As a result, biogenic materials are not a source of new carbon dioxide in the atmosphere.  Municipal solid waste is comprised largely of biogenic materials such as paper, wood, food, leather, cotton, etc.  Our technology has been successfully demonstrated and proven in operating pilot plants.

 
Process Overview

We utilize existing, conventional waste collection, transport, and processing operations to prepare the feedstock material for commercial product development. The bioethanol conversion process includes six major processing areas: 1) feedstock handling and preparation; 2) thermal gasification which produces synthetic gas, or syngas; 3) syngas cooling and cleaning; 4) biocatalytic conversion of syngas to ethanol; 5) electricity generation; and, 6) distillation. 

 
Feedstock Handling (municipal solid waste)

The MSW feedstock is placed and totally contained within an engineered building designed with state-of-the-art ventilation and odor controls, and with a concrete floor to prevent leachate migration.  The feedstock processing operation includes MSW classification, automated conveyor sorting lines, shredding, and waste handling equipment.  Recyclable metals and glass are removed from the MSW feedstock and processed for resale.  Carbon-based MSW and other feedstock materials are mixed, crushed or shredded (minus 6 inches), and fed to the gasification plant for bioethanol production; these materials could include paper, cardboard, wood, food waste, plastic, yard waste, tires/rubber, textiles, and other carbonaceous materials as may be available.  Inert waste materials and residue from the process are removed and hauled to a landfill for disposal or used for other purposes as may be appropriate. 

TYPICAL FEEDSTOCK FLOOR PLAN

CP Manufacturing Inc. provides waste handling design support

Green Energy Production

Gasification of various feedstocks is a mature industry and numerous processes are in use today.  We use commercially available gasifiers which have been used to produce syngas from waste materials and other feedstocks.  There are many gasifiers in operation, several in large metropolitan areas, and all meet EPA and state emission requirements.  The carbon-based feedstock materials are converted to a synthetic gas product (syngas) in the gasifiers using the heat derived from the feedstock and by limiting the available oxygen.  The syngas is derived from the carbonaceous materials and consists primarily of:

►carbon monoxide (CO),

►hydrogen (H₂), and

►carbon dioxide (CO₂); with lesser amounts of:

                                                                                            ►nitrogen (N), and

                                                                                            ►other trace elements. 

Hydrogen and carbon monoxide typically comprise the majority of the syngas and are the components of most value in our process.  Nitrogen is the largest component of the air we breath, comprising about 78% of the volume, and is a harmless gas.  Oxygen comprises about 21% of the air, which is far more oxygen than we use in the gasification process.  Therefore, the amount of air entering the gasifier must be controlled. Carbon dioxide is also present in the air and is produced by animals while breathing, by combustion of fossil fuels in power plants and automobiles, and by burning things like wood, leaves, natural gas, and charcoal, to name a few.  Too much carbon dioxide in the air will trap more energy from the sun, thus contributing to global warming.  Gases such as carbon dioxide and methane are often referred to as "greenhouse gases" because they "trap" heat in the earth's atmosphere.  Our process helps reduce the amount of greenhouse gases in the air.

After the syngas is removed from the gasifier, it is rapidly cooled in conventional heat exchangers.  The heat from the hot syngas is recovered from the heat exchangers and used to produce steam for power generation.  The cooled syngas is then passed through cleaning and scrubbing equipment to remove impurities. 

Our facilities use patented bacteria in low temperature, low pressure fermenters to convert the conditioned syngas into ethanol.  The bacteria are anaerobic and die upon exposure to air.  We refer to this technology as catalytic fermentation.  The conversion process occurs very quickly and is essentially continuous, as opposed to the batch processes required in the corn-ethanol industry.  The bacteria consume most of the syngas in the fermenter.

Multiple gasifiers, cleaning circuits, and fermenters are used in a modular configuration to enhance system selectivity and availability. 

The ethanol is removed from the fermenter as a dilute solution and passed to a distillation tower where it is concentrated to about 95% purity.  The concentrated ethanol is then passed through a molecular sieve to remove the remaining water. The bioethanol is denatured with unleaded gasoline before being stored in tanks for sale as fuel-grade ethanol (over 99% ethanol content).   

The off-gas from the fermenter is further cleaned then routed to a steam boiler for use in power generation.  As mentioned earlier, steam is also generated during the cooling of the syngas. The steam generated at the plant is utilized for heating duties within the process in addition to generating electricity via a steam turbine.
 

Environmental Controls 

Environmental protection measures are implemented for all components of our facility.  The measures are integrated through the design, construction and operation of the waste handling facility, the gasification system, the bioethanol synthesis system, stormwater runoff controls, and the plant grounds as a whole.  The gasifier and bioethanol synthesis system are operated as closed systems – no syngas or other materials can leave the system without treatment.  Our facilities have minimal impact on air quality and meet all local, state, and federal requirements for emissions.

State-of-the-art environmental controls are provided to prevent air, groundwater, and surface water contamination.  Additionally, the facilities are located away from residential areas to prevent noise, odor, traffic, and other possible nuisances to residents.  

Air emissions from waste material off-loading and processing are contained within the waste handling building.  Our facilities store, contain, process, and dispose of solid waste in a manner which prevents threats to human health and the environment, including the creation of fire hazards, vector intrusion, air or water pollution, and other nuisances.  The waste process building is operated with a slight negative pressure to prevent odors and particulates from leaving.  Engineered commercial filtering systems remove odors and contaminants from the building exhaust.
 

The operation of the gasifier is inherently part of the environmental controls.  The design includes carefully controlled syngas velocities, reduced oxygen content, and a slightly negative pressure within the gasifier.  The reduced oxygen atmosphere prevents the formation of oxides and carcinogens such as dioxins and furans.

The raw syngas stream leaving the gasifiers is cleaned and scrubbed to remove contaminants.  Immediately after leaving the gasifier, the syngas is routed through heat exchangers and quench chambers to lower the temperature, then to filters and scrubbers for further cooling and removal of solids and other contaminants.  Multiple processes are used to remove contaminants such as tar, particulates, chlorine, alkali compounds, hydrogen halides, nitrogen compounds, heavy volatile metals, and sulfur compounds.  The fermenter provides additional syngas scrubbing and consumes most of the syngas produced in the gasifier.   Final exhaust gases consist almost totally of carbon dioxide, water vapor, and nitrogen.  

Waste water is treated onsite in our own plant and recycled through the facility to minimize water consumption; fresh water consumption is in the range of 1 to 1.5 gallons per gallon of ethanol produced.