BIOENERGY REFERS to renewable energy from biological sources that can be used for heat, electricity and fuel, and their co-products. Bioenergy can play an essential part in reaching targets to replace petroleum-based transportation fuels with a viable alternative, and in reducing long-term carbon dioxide emissions, if environmental and economic sustainability are considered carefully. Among the different platforms, there are two obvious advantages to using lignocellulosic biomass for ethanol production: higher net energy gain and lower production costs. However, the use of lignocellulosic ethanol as a viable alternative to petroleum-based transportation fuels largely depends on plant biotechnology breakthroughs.
In terms of modern bioenergy, ethanol, biodiesel and biogas are the three major bioenergy products. Ethanol and biodiesel can be used as transportation fuels, and ethanol is also an important raw product in the chemical industry. Therefore, ethanol production has a particularly important role in transforming petroleum-based economies to biomass-based sustainable and environment-friendly economies.
Ethanol can be produced using agricultural products such as starch and sugar, or lignocellulosic biomass. Currently more than 10 billion gallons of ethanol is produced globally per year from starch (maize) and sugar (sugarcane and sugar beet) through mature industrialized procedures, including hydrolysis of starch and fermentation of sugar.
Starch and sugar-based ethanol is often referred to as a first-generation biofuel. Even though the production of ethanol from starch represents the most convenient and technically advanced option for bioenergy but it would result in severe competition between energy and food supplies, which is probably not sustainable in the long term given that the net energy and carbon dioxide balance of the platform is not favorable. Therefore, in temperate regions, biofuel (ethanol for now) production from lignocellulosic biomass represents the best choice if key technical hurdles can be scaled.
Biodiesel is a biofuel requiring far simpler processing technology compared with that required for ethanol. Biodiesel is a mixture of diesel fuel with oils from plant seeds, algae or other biological sources such as animal renderings that have been transesterified for removal of glycerol. A variety of plant species are currently used for biodiesel production including soybean, rapeseed, canola, sunflower and palm.
A third modern choice for bioenergy is biogas, which is produced from a variety of organic wastes, including plant straw, through gasification. Biogases include methane, hydrogen and carbon monoxide. Besides the traditional biogases, hydrogen production by green algae and microbes has been proposed as a potential source for a third generation biofuel. Unlike hydrogen production from other biomass sources, algae-based hydrogen production uses a biological water-splitting reaction, in which hydrogenase uses the photosynthetic electron transport chain to reduce protons for hydrogen production. Hydrogenase engineering for increased oxygen tolerance and systems biology research of genes and pathways involved in hydrogen production are needed to realize the potential of this platform.
Novel enabling biotechnologies are crucial for reducing the costs of bioenergy production, particularly of lignocellulosic ethanol. The key issues include rapid domestication, overcoming recalcitrance, efficient breakdown of cellulose, and increasing biomass and lipid production for ethanol and biodiesel respectively.
Lignin might be the most crucial molecule in need of modification for lignocellulosic feedstocks. It has been established that reducing lignin biosynthesis can lead to lower recalcitrance and higher saccharification efficiency.
Suboptimal water and other abiotic stresses are limiting factors for biomass production; stress tolerance traits are therefore important to enable feedstock to be produced on marginal or sub-marginal lands not favorable for food crops. Drought, metal, salt, cold and heat-stress all induce some similar responses in plants, yet each of these stresses will induce a different set of genes.
Pakistan Agricultural Research Council (PARC), Islamabad has launched a number of projects aimed at cultivating biofuel crops to produce fuel products to enable the country save huge amounts spent on fuel imports. PARC have identified three salt-tolerant plants including Jatropha, Salicornia and Castor, which could grow in salt marshes on sea beaches and could even sustain for five years without water.
Bio-Energy Technology Application Pakistan (BETA PAK) is registered as a partnership company under the Partnership Act 1932 in Pakistan and is working in the field of community based biogas energy development and management. BETA PAK is dedicated to the development and promotion of biogas energy technology and has so far developed and operating hundreds of domestic and dozens of commercial biogas plants all over Pakistan.
Pakistan Council of Scientific and Industrial Research (PCSIR) Karachi along with NED University Karachi is also doing research on algae cultivation in saline water and waste ponds. The cultivation of algae is expected to bring double benefit to the environment in the sense that algae can be used to extract nutrients from waste water, which it converts to fats for biodiesel production and algae extracts pollution from the atmosphere.