Since the energy crises of the 1970s, many countries have utilized biomass as a fuel source to expand the development of its domestic and renewable energy initiatives and reduce the environmental and ecological impact of energy production. Bioenergy accounts for almost 35% of primary energy consumed in developing countries, raising its contribution in the world to 14%. The most important biomass energy sources are wood and wood wastes, agricultural crops and its waste byproducts, municipal solid waste (MSW), animal wastes, waste from food processing, and aquatic plants and algae. The majority of biomass energy is produced from wood and wood wastes (64%), followed by MSW (24%), agricultural waste (5%), and landfill gas (5%). In the industrialized countries, the main biomass processes are expected to be direct combustion of residues and wastes for electricity generation, bio-ethanol and biodiesel as liquid fuels, and combined heat and power (CHP) production from energy crop. For a given biofuel feedstock several issues require careful analysis :
(1) chemical composition of the biomass,
(2) cultivation practices,
(3) availability of land and land use practices,
(4) use of resources,
(5) energy balance,
(6) emission of greenhouse gases, acidifying gases and ozone depletion gases,
(7) absorption of minerals to water and soil,
(8) injection of pesticides,
(9) soil erosion,
(10) contribution to biodiversity and landscape value losses,
(11) farm-gate price of the biomass,
(12) logistic cost (transport and storage of the biomass),
(13) direct economic value of the feedstock taking into account the co-products,
(14) creation or maintain of employment,
(15) water requirements and water availability.
A biofuel is a fuel that immediately derived from living matter. It is produced through modern biological processes, such as agriculture and anaerobic digestion. Biofuels can be derived directly from plants, or indirectly from agricultural, commercial, domestic, and/or industrial wastes. Renewable biofuels generally involve contemporary carbon fixation, such as those that occur in plants or microalgae through the process of photosynthesis. Other renewable biofuels are made through the use or conversion of biomass. This biomass can be converted to convenient energy containing substances in three different ways:
a. Thermal conversion,
b. Chemical conversion,
c. Biochemical conversion. This biomass conversion can result in fuel in solid, liquid, or gas form. This new biomass can also be used directly for biofuels. Bioethanol is an alcohol made by fermentation, mostly from carbohydrates produced in sugar or starch crops such as corn, sugarcane, or sweet sorghum. Cellulosic biomass, derived from nonfood sources, such as trees and grasses, is also being developed as a feedstock for ethanol production. Ethanol can be used as a fuel for vehicles in its pure form, but it is usually used as a gasoline additive to increase octane and improve vehicle emissions. Bioethanol is widely used in the USA and in Brazil. Biodiesel can be used as a fuel for vehicles in its pure form, but it is usually used as a diesel additive to reduce levels of particulates, carbon monoxide, and hydrocarbons from diesel-powered vehicles. Biodiesel is produced from oils or fats using transesterification and is the most common biofuel in Europe. There are various social, economic, environmental and technical issues relating to biofuels production and use, which have been published in the popular media and scientific journals. These include: the effect of moderating oil prices, the "food vs fuel" debate, poverty reduction potential, carbon emissions levels, sustainable biofuel production, deforestation and soil erosion, loss of biodiversity, impact on water resources, rural social exclusion and injustice, shantytown migration, rural unskilled unemployment, and nitrogen dioxide (NO2) emissions.
Author
Shivani kumari, Amity University