BACKGROUND The invasion of water hyacinth (WH) on water bodies comes with adverse consequences for humans and the environment. Using WH as a substrate for affordable and clean energy production is one way of controlling the invasiveness of the aquatic plant. In this study, ensiling was carried out with and without the addition of maize straw (MS) and eggshell powder (ES) to determine the effect of higher total solids (TS) and butyric acid contents on the biomethane potential (BMP) of WH. The silages were stored at ambient temperature for 210 days. The kinetics of biomethane production was determined using three different kinetic models. RESULTS Ensiled WH without MS and ES had a reduced BMP after 210 days. However, a combination of higher TS (40%) and butyric acid contents, resulting from the addition of MS and ES, significantly increased the BMP of WH by 64% after 210 days of ensiling. The kinetic study showed that the dual‐pool kinetic model described the BMP of ensiled and co‐ensiled WH better than the first‐order and modified Gompertz models. CONCLUSIONS Increasing TS and butyric acid contents by co‐ensiling with MS and ES is a low‐cost and sustainable method of enhancing biomethane production from WH. In this way, the invasive nature of WH can be effectively controlled (since a large quantity can be harvested and stored) and circular economy can be enhanced through the effective utilization of waste. © 2022 The Authors. Journal of Chemical Technology and Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry (SCI).

Every year, approximately 35 million tons of combined cassava peels (CP) and cassava wastewater (CWW) are generated from the processing of cassava in Nigeria. The improper disposal of these wastes has serious environmental consequences in the form of air and water pollution. Using these wastes for biofuel production is one way of mitigating the impact of the mass flows on the environment. However, being a lignocellulosic biomass, CP requires pretreatment before it can yield a reasonable amount of biofuel. In this study, ensiling was chosen as a method for the pretreatment of CP slurry (CPS), formed from the combination of CP and CWW, for the production of medium-chain carboxylates (MCCs), which have been reported to be more valuable than biogas and bioethanol. Calcined egg shells (CES) were added to some of the CPS before ensiling, to enhance the formation of butyric acid. The MCCs were produced through batch fermentation of the silage. The results show that ensiling degraded the hemicellulose and cellulose content of CPS. The silage containing CES had greater loss of volatile solids, higher butyric acid content, and a higher MCCs (C6-C8) yield of 210 gkg -1 VS while the silage without CES had an MCC yield of 137 gkg -1 VS. Out of the three kinetic models that were used to predict the production of MCCs, the dual pool model gave the best prediction.

Cocoa pod husks and unripe plantain peels are mass flows that are hugely available in Nigeria without any known industrial application. This study involves the kinetic analysis of the decomposition of hemicellulose into xylose and furfural during the hydrothermal pretreatment of cocoa pod husks and unripe plantain peels within a temperature, time, and solid concentration range of 110 - 140 °C, 5 - 10 minutes and 60 – 100 g/dm3 respectively. The experimentally obtained kinetic constants determined the optimal time for the desired product's (xylose) maximum yield. At the process temperature of 110, 125 and 140 °C, the optimal times were 332, 140 and 79 minutes respectively for the cocoa pod husks, and 210, 117 and 29 minutes respectively for unripe plantain peels. The kinetic models developed from the Response Surface Methodology show that the formation of xylose and furfural from cocoa pod husks and unripe plantain peels depends only on the process temperature and time but not on the concentration of biomass in the reactor. Keywords: lignocellulosic biomass; severity factor; response surface methodology

Kinetic study of microorganism’s growth in chicken manure (CM) when producing biogas is often studied for scale-up purposes. CM are considered as waste, and can cause serious environmental consequences when not properly disposed. The objective of the study is to know the characteristics of the bioreactor condition or environment responsible for CM degradation and biogas production. Methods involves serial dilution, pour plating, cell count and the determination of Monod parameters. POLYMATH regression results shows that CM of particle density 0.0163 g/cm3 gives a maximum specific growth rate, ?_max of 0.007316 hr^(-1) and half saturation constant, K_s of 3.8×?10?^8mg/l which points to substrate sufficiency for the survival of microorganisms and biogas production.

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