Water hyacinth (Eichhornia crassipes), an invasive water weed with a large biomass, poses serious socioeconomic and environmental challenges in fresh water bodies. Efforts to control and remove water hyacinth (WH) can be complemented by biogas production, which, however, requires knowledge of its chemical and nutritional composition. Moreover, codigestion with other substrates may compensate for possible limitations of its largely lignocellulosic biomass. This study carried out proximate, crude fiber, elemental and biochemical analysis of WH and a co-substrate, ruminal slaughterhouse waste (RSW). The WH had significant concentrations of cellulose, hemicellulose and carbohydrates of 331,200, 231,800 and 447,800 mg/L, respectively, and lesser concentration of lignin of 99,400 g/L that is desirable in biomass for biogas production. Concentrations of C, N, P and K in WH were 15,480, 1654, 51 and 137 mg/L compared to 26,220, 1390, 34 and 7475, respectively, for RSW, which indicated potential for biogas generation. The potassium concentration for WH of 137 mg/L was below the optimum range of 200-400 mg/L while that for RSW of 7476 mg/L was in the inhibitory range. Both biomass exhibited phosphorous deficiency at C/P of 310 and 656 for WH and RSW, respectively, against optimum ratio of 100 and 150 for hydrolysis and acidogenesis stages and methanogenesis stage, respectively. The C/N for WH of 9.4 was at the lower limit for optimal biogas production of 8 mg/L that demarcates potential ammonia toxicity while that for RSW of 18.8 was near the upper limit of 20 mg/L for nitrogen deficiency. Co-digesting the two substrates has the potential for balancing potassium concentrations and the C/N ratios. Trial co-digestion of WH with RSW improved WH gas production demonstrating complementary effect of the two substrates. However, commercialization of the codigestion would need to establish the optimal mix proportions and methanogenic microbial communities involved in the digestion process.

The use of biomass as renewable energy source is of interest in reducing dependence on fossil fuels and associated impacts of climate change. Water hyacinth (WH), an invasive aquatic plant of environmental concern has large biomass that is available for biogas production. Co-digestion of this largely lignocellulose biomass with other substrates may correlate process parameters and improve biogas production. This study evaluated co-digestion of WH biomass with various mix proportions of ruminal slaughterhouse waste (RSW) at 24, 32 and 37°C in order to assess the optimum proportion and temperature. The rate of biomethanation increased with temperature from 0.23 at 24ºC to 0.75 and 0.96 at 32ºC and 37ºC, respectively, and similarly methane yield improved from 14 at 24ºC to 40 and 52 L/kg air dried water hyacinth at 32ºC and 37ºC respectively. A WH: RSW ratio of 30% showed optimum acclimatization and methane yield in a residence time of 60 days. The duration of the initial drop in pH that indicates hydrolysis stage decreased with increase in proportion of RSW, indicating faster hydrolysis and fermentation processes. Longer and stable latter alkaline pH zone suggested improved biomethanation and greater biogas production. Co-digestion with 30% RSW at 24ºC improved biogas yield by 75% from 8.05 to 14.09L/Kg biomass, methane component of biogas by 9% from 59 to 68% and reduced the retention time for substrate by 36%, suggesting synergy in co-digestion with respect to biogas quality. Changing the temperature from 24 to 32ºC increased the yield by 186% and reduced retention time by 73%. The results demonstrated synergy in co-digestion of the two substrates and the process dynamics that are useful in a possible process commercialization. ©2019. CBIORE-IJRED. All rights reserved

The production of electrical and electronic equipment (EEE) that include computers, mobile phones, modems, printers, refrigerators, and air conditioning units has been growing rapidly stimulated by technological advances, increased product affordability, and short product lifespans. However, this growth has not been matched by recognition of the dangers to health and the environment from disposal of the waste EEE (e-waste) especially in developing countries. Globally, the annual generation of e-waste is in the range 20 -50 million metric tons, which, following the current trend can increase to over 120 million metric tons by year 2050. This paper reviews the nature, complexity and health and environmental impacts of the e-waste, its global scale, and the alternative technologies for its management. However, the focus is on developing countries, which import disproportionately large quantities of used and obsolete EEE for reuse and recycling but lack effective legislation, skills and infrastructure for management of the waste. As a result, e-waste handlers and recyclers use crude methods for recycling oblivious of the inherent dangers of heavy metals and organic substances in the waste. While the exporting of EEE to developing countries for reuse extends their useful life, informal recycling and final disposal through open dumping, burning and burial poses danger to human health and the environment. Electronic products contain many materials requiring special end-of-life handling; mainly, lead, mercury, arsenic, chromium, cadmium, and plastics that are capable of releasing, dioxins and furans among other compounds. Consequently, successful management of the e-waste in the developing countries will require institution of guiding framework for end of life management such as the extended producer responsibility, and product take back. Ultimately, the key to successful e-waste management is the development of formal recycling facilities. Centralized collection points where economies of scale will attract investment for facilities for dismantling and disassembling of component for recycling and for disposal of toxic components are recommended.