Tag Archives: biomass

Anaerobic digestion solution for waste & energy

Anaerobic digestion

Anaerobic digestion (AD) can be used for farms, businesses and municipalities as a productive solution to a growing waste problem throughout the world. In addition to AD, waste-to-energy is done in landfills using landfill refuse and landfill gases (such as methane). The use of AD in a biomass plant is a cost-effective way to produce renewable energy. AD also leads to less landfill waste and is a constructive way for farms, businesses and municipalities to dispose of waste. AD is the process of turning agricultural waste (such as livestock manure), wastewater, or municipal, commercial and industrial waste streams (such as food processing waste), into energy. AD uses micro-organisms to break down organic material and create biogas (biogas consists mostly of methane and CO2).

Instead of waste simply ending up in landfills, or being incinerated, waste can be turned into energy. Farms can be entirely powered by waste from their livestock, food waste and wastewater. Use of AD can make also make wastewater treatment facilities energy neutral or even energy positive, translating to huge cost savings for municipalities.

Organic waste finds a purpose in an AD biogas plant, as it is put in a digester, along with various types of micro-organisms (enzymes, bacteria etc…), to transform the waste into energy (methanation). The molecules of the organic material are broken down in the plant into a useful form like glucose. The “digested” raw material is then used to create biogas (and digestate which can be used as fertilizer).

The biogas can then be purified (and also optionally be upgraded with hydrogen) and turned into pipeline-quality synthetic natural gas for the grid. Biogas can also be turned into compressed natural gas (CNG) for vehicles. The anaerobic process also occurs naturally (as in landfills), in addition to the man-made construct in a biomass plant.

An anaerobic digester and biomass plant generate biogas (and/ or biomethane) which can be burned on-site to generate heat, power or both (so, combined heat and power – CHP). AD is mostly used by farms and wastewater treatment facilities for on-site electrical and heating generation, although it can also be used in a variety of other applications. Biogas can also be purposed as an energy source for the grid when purified, and turned into pipeline-quality synthetic natural gas (or turned into biomethane and used for heat or transportation as CNG). Also produced in the process is digestate, which is a source of nutrients that can be used as a fertilizer.

Biogas can also be upgraded with hydrogen, combining the outputs of a biogas plant and an electrolyzer, creating biomethane. Like conventional natural gas, biomethane can be used as a transportation fuel in the form of compressed natural gas (CNG), or liquefied natural gas (LNG). When biogas is used for heat or transportation, as biomethane, CNG, (biomethane – CNG – can be used in place of diesel, given modifications to the vehicles in question), there are tremendous greenhouse gas reductions.

The entire bus fleet in Oslo, Norway, is run on CNG from sewage treatment and organic waste, and they see a dramatic (around 70%) reduction in greenhouse gas (GHG) emissions compared to fossil fuel burning vehicles. Food waste and other waste processed through AD also brings the benefit of reducing GHG emissions substantially by reducing landfill waste. When AD is used for on-site electrical generation, energy generation for a municipality, farm or wastewater facility, GHG emissions overall are greatly reduced. Energy produced by AD has a very low overall carbon footprint.

Poplars AD plant

Poplars AD plant

The AD plant at Cannock, Staffordshire, England (called the Poplars AD plant) is an example of a successful, large-scale AD plant. The £24 million project treats commercial and industrial food and waste to create, through methanation, around 6MW of renewable energy, synthetic natural gas, for the national grid. The Poplar plant shows that a large-scale anaerobic digestion project is viable. AD has been successful in many commercial operations as well. For example in Orlando, Florida, food waste sourced primarily from the Walt Disney World Resort is fed through an anaerobic digester, producing enough electricity to meet the needs of over 16,000 homes.

Please see: renewable energy: biomass and biofuel

Gasification – syngas from fossil fuels and environmentally friendly versions

Algae : the future of biofuel

Cellulosic biofuel – one fuel option

Gasification Applications Chart

Gasification – syngas from fossil fuels and environmentally friendly versions

The creation of syngas (or synthetic natural gas) is a technology based on coal gasification for the majority of plants, although it can also be based on biomass or other, fossil, fuels. Since it is also usually based on a nonrenewable fossil fuel, and usually involves the emission of greenhouse gasses like CO2, it can’t be described as a “green” technology. However, when coal gasification is used in conjunction with carbon capture and storage (CCS), or a green technology like integrated gasification combined cycle (IGCC), or when syngas is created using biomass, the technology is certainly “greener” than burning a fossil fuel. IGCC is a fairly new technology that uses a gasifier in converting coal and biomass into syngas, and has come to be known as “clean coal”. Syngas plants use coal gasification for the most part, but to make the production of syngas greener, use of IGCC or biomass must be implemented.

Lignite, a brownish type of coal, is most often used as a source in the process of creating syngas. Gasification uses the coal, steam and oxygen to create syngas — mostly hydrogen and carbon monoxide. The syngas can then be burned directly to create energy used to generate electricity or heat homes and businesses, convert the syngas into “substitute natural gas”, or can be used to create products including methanol, nitrogen-based fertilizers and hydrogen for oil refining and transportation fuels. Coal gasification is sometimes called “clean coal” because it can create energy with less harm to the environment than traditional fossil fuel use.

A significantly more environmentally friendly version of gasification, other than coal use, is available in biomass. Biomass gasification uses a feedstock as in agricultural residues (like wheat and straw), energy crops (like switchgrass), forestry residues and urban wood waste (for example, from construction sites).

The leading region in the world for syngas production is Asia/ Australia, in particular China. China mostly uses coal for its syngas production, relying on their vast coal deposits, thus still producing significant quantities of greenhouse gas emissions. China is trying to rely more on domestic sources for gas and less on importing liquefied natural gas. A significant number of gasification plants are found in India, South Korea, Taiwan and Singapore.

The Africa/ Middle East region also produces a significant quantity of syngas, more than Europe. However, production of syngas in Europe uses a wider selection of feedstocks, technologies and products than other regions. The coal-based units primarily utilize IGCC technologies. There are petroleum, natural gas and biomass plants that produce either power or chemicals. A fairly new plant in Swindon, England illustrates the advancements that European nations are making with gasification. Methanization is used to transform gasified biomass into grid-quality syngas, the biosynthetic natural gas then providing power to the grid.

Most syngas production in North America lies within the United States. These plants include: natural gas facilities that primarily produce chemicals, coal and petroleum plants that produce either power, chemicals and fertilizers or syngas, including a couple of IGCC plants. In Canada, gasification is used to produce hydrogen and power to upgrade synthetic crude oil from the tar sands.

From: http://www.greencitytimes.com