Sustainable Energy 2010–2020 explains how to produce cleaner energy and promotes distributed combined heat and power generation with fuels from renewable sources and waste.
“Renewable natural gas” is pipeline-quality natural gas that is created from renewable resources such as timber industry waste, crop residues, municipal waste, seaweed and algae.
Benefits of increasing the manufacture and use of “renewable natural gas” are:
- Faster take-up of distributed energy generation technology.
- Low-cost carbon dioxide capture.
- Opportunities to participate in the manufacture and export of related technology and by-products.
- Rapid reduction in carbon dioxide emissions.
Faster Take-Up of Distributed Generation Technology
The Australian Capital Territory uses landfill gas to generate electricity at its Mugga Lane landfill site: (See the ACT Sustainability and the Environment Commissioner report here and the Clean Energy Council website here.) This landfill gas is about 50% by volume carbon dioxide that must be removed if the methane component is to be made suitable for distribution through the natural gas network.
Cleaning this landfill gas to pipeline quality will allow it to be used far more efficiently. At present the landfill gas is burned in diesel-electric generators and over 50% of its available energy is wasted as heat.
Ceramic Fuel Cells Limited (Melbourne, Australia) is a global leader in fuel cell development. Its “BlueGen” ceramic fuel cell product for installation into homes and other buildings convert natural gas into electricity and heat. The grid-connected units, which are about the size of a dishwasher, are highly efficient and cut carbon dioxide emissions by up to 75% compared to Victoria’s current brown coal power stations: (See Ceramic Fuel Cell's product description for BlueGen here.)
Giving environmentally-aware consumers the choice to buy “renewable natural gas” will encourage the acceptance of this efficient fuel-cell technology. At present energy consumers may elect to buy electricity produced from renewable energy resources. A similar option for natural gas is highly desirable.
The Department of Energy and Climate Change in Great Britain (DECC) considers that biogas produced from renewable sources, by anaerobic digestion or gasification of biomass materials, can contribute significantly to the UK’s renewable energy targets. (See "England's Official Information Portal on Anaerobic Digestion" on "Non-conventional sources of gas" here.)
On 29 December 2009 DECC published a document entitled "Biomethane into the gas network: a guide for producers" in support of the UK Renewable Energy Strategy. It outlines the main legal, technical and regulatory requirements specific to the gas market in Great Britain. The purpose is to help UK producers of biogas who may not have considered injecting it into the gas grid to make an informed choice between the various marketing options.
A similar guide adapted to the gas market of Australia is desirable.
Low-Cost Carbon Dioxide Capture
Capturing highly concentrated carbon dioxide from raw natural gas and biogas is simple and inexpensive: (For one example, see the Natural Gas Supply Association's website here.) In contrast, capturing carbon dioxide that is mixed with the exhaust gases of fossil-fuelled power stations is yet to be proven to be commercially viable.
Carbon dioxide produced from natural gas can be sold as it has a number of commercial applications.
The separation and capture of carbon dioxide from biogas provides a cost-effective method for lowering atmospheric carbon dioxide levels.
Opportunities in Related Technology
Carbon dioxide separation from biogas and raw natural gas is carried out on a large-scale in gas refineries and also in small-scale processing plants. A number of techniques are used commercially –
- Xebec Adsorption Inc. of Blainville, Quebec, Canada supplies integrated biogas plants to upgrade biogas to purified biomethane meeting pipeline or compressed natural gas quality specifications.
- The plants convert the methane gas into natural gas energy using Xebec Adsorption Inc. technology: (See the Xebec Inc. website here.) The first landfill gas recovery facility at Rumpke Sanitary Landfill opened in 1986, the second plant opened in 1995 and the third plant opened in 2007. The facilities have the potential to recover millions of cubic metres of landfill gas daily. Its recovery operation is the largest landfill gas-to-pipeline facility in the world. The plants combine to provide enough natural gas energy for about 25,000 homes and businesses. The natural gas is distributed by Duke Energy Corp.
- Technology collaboration offer - Cryogenic upgrading of biogas to natural gas or Liquefied Natural Gas (“LNG”) with CO2 utilisation.
- A Dutch Small-Medium Enterprise has developed an innovative technology to upgrade biogas to natural gas quality and at the same time produce liquid CO2 of industrial quality. It can be applied at any biogas producing installation and the CO2 can be used in greenhouses, etc. The company is looking for well established partners in the energy sector with extensive knowledge of the local markets. A license agreement and a commercial agreement with technical assistance are offered for cooperation: (See the Enterprise Europe website here.)
Existing natural gas refineries and Liquefied Natural Gas (“LNG”) plants that separate carbon dioxide from “raw” natural gas can also be used to extract carbon dioxide from biogas and “synthetic natural gas” (i. e. gas derived from fossil fuels such as brown coal) .
Biogas production from waste materials and renewable bio-fuel crops is a rapidly growing segment of the renewable energy sector. Four examples of this technology are –
- GreatPoint Energy of Cambridge, Massachusetts is a natural resources company and the developer of a highly-efficient catalytic process known as hydromethanation by which coal, petroleum coke and biomass (wood waste, municipal solid waste, and energy crops such as poplar and switch grass) are converted directly into low-cost, clean, pipeline quality natural gas. GreatPoint Energy is able to reduce the operating temperature in the gasifier while directly promoting the reactions that yield methane. Under these mild “catalytic” conditions around 400°C, less expensive reactor components can be utilized, pipeline grade methane is produced, and very low-cost carbon sources (such as lignite, sub-bituminous coal, petroleum coke and biomass) can be used as feedstock. Roughly half the carbon in the feedstock is removed for capture as a pure CO2 stream suitable for sequestration: (See GreatPoint Energy website here.)
- Diversified Energy Corporation of Gilbert (a suburb of Phoenix), Arizona is commercialising its OmniGas™ molten-metals based gasification technology that uses a 1300°C molten slag to gasify a wide range of hydrocarbon feedstocks (e.g., biomass, coal, petroleum coke, and wastes) for the production of an ultra-clean synthetic natural gas: (See Cleantech.com news report here.)
- Sundrop Fuels Inc of Louisville, Colorado is constructing a high-temperature solar-thermal biomass gasifier for converting almost any kind of biomass into clean bio-fuels. Mirrors focus enough solar radiation to raise the temperature of the gasifier to nearly 1300°C, high enough to gasify any plant material: (See Biofuelsdigest report here.)
- Genifuel Corporation produces renewable natural gas from wet organic material by a highly efficient process known as Catalytic Hydrothermal Gasification (CHG). The Genifuel process starts with wet organic material, either photosynthetic biomass such as algae and other water plants, or other wet material such as wastewater solids or food processing wastes. The process also works extremely well with wet wastes from other biofuel processes such as algae biodiesel production or corn ethanol production. The organic material is collected and then gasified in the Catalytic Hydrothermal Gasifier, which achieves very fast conversion of more than 99% of the organic content of the wet biomass. (See Genifuel website here.)
These technologies can produce natural gas from a very wide range of materials that are presently considered to be waste. Fossil fuels such as brown and black coal can also be converted to natural gas with the same technologies. This means that the benefits of distributed energy generation can be achieved quickly and the fossil fuel component reduced over time without any reliance on new and expensive infrastructure.
At present the Lower Molonglo Water Quality Control Plant in the Australian Capital Territory incinerates over 45 tonnes of sewage sludge every day: (See ActewAGL wastewater treatment process here.) In every city in the world a huge volume of plastics and other non-biodegradable materials are added to landfills or pollute waterways. These are quite suitable for gasification.
In Australia each year some twenty million tonnes of forest litter may be burnt annually in prescribed burning (estimated at the rate of 20 tonnes per hectare): (See Australian Government environment report here.) The opportunity exists to develop an environmentally sound harvesting technique to gather some of this forest litter. If successful this technology would provide a better solution to bushfire hazard reduction than prescribed burning while at the same time producing feedstock for gasification by the renewable energy industry.
Rapid Reduction in Carbon Dioxide Emissions
Significant benefits will result from the take-up of this distributed generation and gasification technology.
For instance: when just 25% of world stationary energy requirements are produced from renewable sources it is possible to capture 100% of the carbon dioxide produced by coal-fired power stations.
How can this be?
- The Ceramic Fuel Cells Limited “BlueGen” product is twice as efficient as large central power stations. This means that only 50% of the quantity of coal is required to deliver the same final amount of energy to consumers. In other words the problem is halved simply by using efficient fuel cells and distributing the generation of electricity and heat to where it is needed.
- (The energy that now requires 4 tonnes of carbon to be burned in a central coal-fired power station can be produced from just 2 tonnes of carbon.)
- The technologies available for gasification of biomass, waste material and coal result in the separation of 50% of the carbon in the feedstock as carbon dioxide.
- (The energy content of every 2 tonnes of carbon in the feedstock to a gasifier is transferred into just 1 tonne of carbon in the form of pure methane. The other 1 tonne of carbon is separated simply and cheaply as pure carbon dioxide.)
- When half of the energy in synthetic natural gas is coming from biomass and the other half is coming from coal, then the carbon dioxide that is separated contains the equivalent of 100% of the carbon that came from coal.
- (For every 2 tonnes of carbon fed into a gasifier, when 1 tonne of this carbon comes from coal, then the equivalent of ALL of that 1 tonne of carbon is simply and cheaply captured as carbon dioxide.)
All plants extract carbon dioxide from the atmosphere by photosyntheses and can be a source of biomass feedstock for the production of renewable natural gas. Some of this carbon dioxide extracted by plants can be permanently removed from the earth’s atmosphere if it is sequestered once separated from biomethane during the production of renewable natural gas.
As soon as slightly more than 1 tonne out of every 2 tonnes of carbon fed into gasifiers is coming from biomass, then the carbon dioxide that is captured will begin reducing the atmospheric concentration of carbon dioxide.
We can reach this point – beginning to lower atmospheric carbon dioxide levels – as soon as we can achieve the production of just 25% of centralised energy generation from renewable biomass sources and with combined heat and power distributed energy generation.
© GerbilNow, March 2010