Biomass and Waste to Energy

Biomass is a term used in several contexts: in the context of ecology it means living organisms, and in the context of bioenergy it means matter from recently living (but now dead) organisms. In the latter context, there are variations in how biomass is defined, e.g. only from plants, or from plants and algae, or from plants and animals. The vast majority of biomass used for bioenergy does come from plants. Bioenergy is a type of renewable energy with potential to assist with climate change mitigation. 

Biomass used for energy production or in other words: biological mass used as a renewable energy source (usually produced through agriculture, forestry or aquaculture methods)

Biotechnology

Biomass is also used as a term for the mass of microorganisms that are used to produce industrial products like enzymes and medicines. 

Bio-Products

Examples of emerging bio-products or bio-based products include bio-fuels, bio-energy, bio-char, starch-based and cellulose-based ethanol, bio-based adhesives, bio-chemicals, bio-plastics, etc. 

Biological wastewater treatment

In biological wastewater treatment processes, such as the activated sludge process, the term "biomass" is used to denote the mass of bacteria and other microorganisms that break down pollutants in wastewater. The biomass forms part of sewage sludge.

Waste-to-Energy

Waste-to-energy (WtE) or energy-from-waste (EfW) is the process of generating energy in the form of electricity and/or heat from the primary treatment of waste, or the processing of waste into a fuel source. WtE is a form of energy recovery. Most WtE processes generate electricity and/or heat directly through combustion, or produce a combustible fuel commodity, such as methane, methanol, ethanol or synthetic fuels. 

Gasification and pyrolysis processes have been known and used for centuries and for coal as early as the 18th century.... Development technologies for processing [residual solid mixed waste] has only become a focus of attention in recent years stimulated by the search for more efficient energy recovery. (2004)  

Methods

Incineration

Incineration, the combustion of organic material such as waste with energy recovery, is the most common WtE implementation. All new WtE plants in OECD countries incinerating waste (residual MSW, commercial, industrial or RDF) must meet strict emission standards, including those on nitrogen oxides (NOx), sulphur dioxide (SO2), heavy metals and dioxins. Hence, modern incineration plants are vastly different from old types, some of which neither recovered energy nor materials. Modern incinerators reduce the volume of the original waste by 95-96 percent, depending upon composition and degree of recovery of materials such as metals from the ash for recycling. 

Incinerators may emit fine particulate, heavy metals, trace dioxin and acid gas, even though these emissions are relatively low from modern incinerators. Other concerns include proper management of residues: toxic fly ash, which must be handled in hazardous waste disposal installation as well as incinerator bottom ash (IBA), which must be reused properly. 

Critics argue that incinerators destroy valuable resources and they may reduce incentives for recycling. The question, however, is an open one, as European countries which recycle the most (up to 70%) also incinerate to avoid land filling. 

The method of incineration to convert municipal solid waste (MSW) is a relatively old method of WtE generation. Incineration generally entails burning waste (residual MSW, commercial, industrial and RDF) to boil water which powers steam generators that generate electric energy and heat to be used in homes, businesses, institutions and industries. One problem associated is the potential for pollutants to enter the atmosphere with the flue gases from the boiler. These pollutants can be acidic and in the 1980s were reported to cause environmental degradation by turning rain into acid rain. Modern incinerators incorporate carefully engineered primary and secondary burn chambers, and controlled burners designed to burn completely with the lowest possible emissions, eliminating, in some cases, the need for lime scrubbers and electro-static precipitators on smokestacks.

By passing the smoke through the basic lime scrubbers, any acids that might be in the smoke are neutralized which prevents the acid from reaching the atmosphere and hurting the environment. Many other devices, such as fabric filters, reactors, and catalysts destroy or capture other regulated pollutants. According to the New York Times, modern incineration plants are so clean that "many times more dioxin is now released from home fireplaces and backyard barbecues than from incineration." According to the German Environmental Ministry, "because of stringent regulations, waste incineration plants are no longer significant in terms of emissions of dioxins, dust, and heavy metals".

Compared with other waste to energy technologies, incineration seems to be the most attractive due to its higher power production efficiency, lower investment costs, and lower emission rates. Additionally, incineration yields the highest amount of electricity with the highest capacity to lessen pile of wastes in landfills through direct combustion. 

Fuel from plastics

It aims to solve major environmental issues namely pollution caused due to plastic waste accumulation and the need for an alternative fuel source. The process that is used to convert plastic into fuel is pyrolysis. It is the thermal decomposition of materials at very high temperatures in an inert atmosphere. It involves change of chemical composition and is mainly used for treatment of organic materials. In large scale production, plastic waste is ground and sent for melt feeding and then the process of pyrolysis takes place, catalytic converters helps in the process and the molecular rearrangement of polymers takes place, the vapours are condensed with oil or fuel and accumulated in settling tanks and filtrated, fuel is obtained after homogenation and can be used for automobiles and machinery. It is commonly termed as thermofuel or energy from plastic. 

Other

There are a number of other new and emerging technologies that are able to produce energy from waste and other fuels without direct combustion. Many of these technologies have the potential to produce more electric power from the same amount of fuel than would be possible by direct combustion. This is mainly due to the separation of corrosive components (ash) from the converted fuel, thereby allowing higher combustion temperatures in e.g. boilers, gas turbines, internal combustion engines, fuel cells. Some are able to efficiently convert the energy into liquid or gaseous fuels:

*Source-Wikipedia.