Nigeria is a country blessed with abundant energy resources. These are the primary energy sources such as crude oil, natural gas, coal, and renewable energy most of which are underutilized such as hydro, wind, solar, biomass, and fuel wood. Most of the energy needs of Nigerians for household and industrial use are petroleum-based namely petrol, diesel, kerosene, and natural gas. While kerosene and gas are used extensively by most households in urban areas, the rural dwellers, which form 70-80% of the population, depend almost exclusively on fuel wood for household use. This high dependence on fuel wood for domestic and commercial purposes is a matter of public concern as it is the major cause of deforestation in many parts of the country and with implications cause of global warming. Since the rate of regeneration of wood is not commensurate with the high rate of consumption, there is an increasingly high rate of desert encroachment, soil erosion, and loss of soil fertility in places with high rates of deforestation. Thus complete reliance on fuel wood to meet the domestic energy needs of rural communities enhances environmental degradation - a situation that is very difficult to reverse. One of the ways of saving the environment from further deterioration and also supplementing the energy needs is by the production and use of biogas by the rural communities. The technology of biogas production is not new. The development and construction of biogas digester started in the I920s and has spread to several developing countries such as India, Taiwan, etc. In these countries, biogas technology has supplemented a large proportion of the energy requirements of the rural majority. The availability of raw materials coupled with the ever-increasing prices of fossil fuel has made this technology attractive.

Energy consumption has increased steadily over the last century as the world population has grown and more countries have become industrialized. Biogas, a renewable biofuel is becoming increasingly important as a consequence of major concerns for depleting oil reserves, rising crude oil prices, and the greenhouse effect. A lignocellulosic feedstock is considered an attractive raw material because of its availability in large quantities at low cost (Mosier et al., 2005) not only for the liquid transportation fuel but also for the production of chemicals and materials, i.e. the development of carbohydrate-based biorefineries (Machunga-Disu et al., 2012). Besides terrestrial plants, aquatic plants are also promising renewable energy resources. Water hyacinth, Eichhornia crassipes is such an aquatic plant.

Biomass is an important renewable resource that may replace petroleum-based energy and chemicals (Han, 2013 and Yoon, 2014). However, global warming and depleting crude oils have compelled us to switch towards renewable energy. Some plants like water hyacinth(Eichhornia crassipes) quickly grow to very high densities (over 60 kg/m2), thereby completely clogging water bodies (Julien, 1996). The mixture of animal waste and water hyacinth resulted in better biogas yields (Kumar, 2005) and the sludge obtained from mixed feed had better nitrogen, phosphorus and potassium content which could serve as very good manure. Water hyacinth proved to be a promising substrate for anaerobic digestion with its digestion resulting in high biogas yields (267 L/kg VS) (O’Sullivan, 2010).

Water-hyacinth is an invasive alien species in waterways. According to MWBP/RSCP (2006), the International Union Conservation of Nature (IUCN) identified the plant as one of the 100 most aggressive invasive species. While the study conducted by Gichuki et al., (2012) recognized the plant as one of the top ten (10) worst weeds in the world. The plant is also listed by law in Africa as a pernicious weed with the widest spread damaging aquatic plant species. UNEP (2012), reported that the plant is difficult to manage and control, thereby threatening economic development (Alimi and Akinyemiju, 1991), human well-being (Toftet al., 2003; Hellman et al., 2008 and Varshney et al., 2008) and biodiversity (Villamagna and Murphy, 2010); thereby flourishing continuously in all surfaces of freshwater, wetlands, and estuaries, appearing in cluster population and forming a heavy dense mat. In Nigeria almost all river bodies have been dominated by water hyacinth. Cossil et al., (2001) documented that the plant proliferation resulted in the reduction of maritime business, irrigation, house boat rental services, access to water for riverine settlement and recreational activities; thereby, increasing evapo-transpirational as well as fish losses (Irving and Beshir, 1982). Studies have revealed that human activities (Dagno et al., 2012) have led to the spread of the plant as well as the lack of naturally occurring enemies that are capable of suppressing their spread. Shoeb and Singh (2002), ascertained that when conditions are favourable the plant can flourish well and can reach a mass density of 17.5 metric tonnes per hectare per day, and by conversion this value is equivalent to 6387.5 metric tonnes per hectare per annum thus its need in biogas production. Studies have also revealed that to keep the plant at an unproblematic level, the control methods that are often used includes physical – mechanical (Patel, 2012), biological (Simberlof and Sliling, 2003; Dagno et al., 2012 and Venter et al., 2012) and chemical (UNEP, 2013) methods. Therefore, the plant has found application in fire board production, organic fertilizer production, rope making, paper production, animal fodder, mat and basket making, water purification, fish feed formulation, charcoal briquetting, remediation of crude oil contaminated soil and bio fuel production such as biogas, bio-ethanol and biodiesel (Jayaweera et al., 2007; Almoustapha et al., 2009; and Kunatsa and Mufundirwa, 2013). According to Wang and Calderon (2012), water hyacinth can be a potential resource to produce biogas and bioethanol as supported by other researchers (Akinwande et al., 2013; Gunnarsson and Petersen 2007; Cheng et al., 2010 and Kunatsa and Mufundirwa, 2013). According to Zulu and Richardson, (2013), it can therefore, be a good alternative for the production of energy as more than 80% of urban households in sub- Saharan Africa use charcoal as their main source of cooking energy.