Co-digestion Of Agricultural Wastes Research Articles

Production of Biogas from Mono- and Co-Digestion of Agricultural Waste (Cow Dung, Chicken Dropping, and Rice Husk)

This study focused on waste to energy technology that utilized mono- and co-digestion of cow dung (CD), chicken dropping (ChD), and rice husk (RH). The fabricated digesters were assessed for the influence of temperature and pH on biogas production from the materials used. The total aerobic bacteria and fungi counts for the mono- and co-digestion of cow dung with chicken droppings had highest number on day zero (1.5x107cfu/ml, 1.6x105cfu/ml and 1.4x108cfu/ml, 1.2x105, respectively), while the lowest counts were recorded on the 35th day (1.3x101cfu/ml, 1.0x101cfu/ml and 1.1x101cfu/ml, 1.0x101cfu/ml, respectively). The highest count of the acetogenic organisms was 1.8x105cfu/ml on the 18th day whereas no count was observed on the 35th day. Methanogenic bacteria had a count ranging from 1.0x 101 cfu/ml to 3.4x104cfu/ml on the 18th day. pH was within the range of 5.3 – 8.5 in the digesters. Cow dung (100% CD) showed the highest cumulative gas production of 41.65m3 compared with chicken droppings (100% ChD) and rice husk (100% RH) which showed values of 8.91 m3 and 0 m3, respectively, within temperature. Furthermore, the co-digestion of 75% CD + 25% ChD, 50% CD + 50% ChD, 25% CD + 75% ChD, 50% CD + 50% RH, and 50% ChD + 50% RH produced biogas values of 20.1m3, 15.13m3, 7.51m3, 5.1m3, and 2.09m3, respectively, at the same temperature range of 36.2OC - 41.7OC.
 The assay for nitrogen (N), phosphate (P), potassium (K) and sulphate (S) to find the major plant nutrient from the digestate showed that 100% CD was richer in N (1.8mg/l), P (0.5mg/l), and S (0.5mg/l) than the other biomass types, whereas 50% CD 50% ChD had the highest content of P. The present study suggests that the digestion of cow dung, chicken droppings, and rice husk can be an effective means of waste management, pollution control, and generation of renewable energy (biogas) and fertilizers, thereby further strengthening the role of agriculture in the area of food security.

Impact of supplementary nutrients on codigestion of agricultural waste: Study of temperatures

Different wastes treated together can be the supplement of nutritional deficiencies for the microorganisms involved in anaerobic codigestion (AcoD). In this study, the presence of macromolecules and trace elements on AcoD of agricultural waste was assessed. An extra nutrients solution that plays a key role in the microbiological metabolism was used at three different conditions: mesophilic (35°C), intermediate (42°C) and thermophilic (55°C). The main results showed that at 35°C in the presence of nutrients, biogas production reached 1.5-fold the production of biogas without them. Additionally, productivity was 1.9 times higher than that for the process without nutrients.Also, 42°C without nutrients posed an interesting approach due to the uncommon use of this intermediate temperature, which has been demonstrated to be worth considering (55% of VS removal and 7.4 L-biogas). The AcoD at 55°C showed that biogas production also surpassed 10.2L with nutrients and that mL-CH4/g-VS were 1.2-fold of that obtained for the process without extra solution. Results for each temperature indicate that the nutrients solution contributes to AcoD. Furthermore, 35°C, the most widespread temperature range at industrial scale, was the temperature at which the impact of nutrients was more remarkable. A deeper knowledge of AD nutritional limitations according to temperatures can optimize the industrial process in order to get better biogas yields and biomass removal.

Biomethane Production from Co-digestion of Banana Peel and Waste Glycerol

Banana peel and biodiesel derived glycerol are one of the most abundant agricultural waste in Southeast Asian countries. This current research demonstrated potential biomethane production from co-digestion of agricultural wastes under mesophilic fermentation. The wastes used include (1) banana peel (varying total solids in the range 2.5-10% w/v) and (2) Banana peel mixed with pure or waste glycerol. All treatments were setup in duplicate in 0.5 L batch reacotr. Gas and liquid samples were collected every 12 and 24 hr, respectively. Maximum methane production potential and yield were 181 mL and 188mL g-1 TS at 7.5% banana peel. The maximum methane production potential and yield of 7.5% banana peel mixed with 7.5 g L-1 pure glycerol (in the presence of buffer) were 467 mL and 151 mL g-1 COD, respectively, while those of 7.5% banana peel mixed with 7.5 g L-1 waste glycerol (in the presence of buffer) were 652 mL and 281 mL g-1 COD, respectively. Small amount of VFAs and ethanol was accumulated in the reactor content. The current findings indicate the potential use of glycerol waste as a co-substrate in biomethane production.