A modified digester prototype to produce biogas from some agricultural wastes as a renewable energy resource

Abstract EN

The world is rapidly depleting its supply of natural gas as one of the fossil fuels.

At the same time there are millions of tons of biomass waste being produced every year which disposal is a problem.

Biomass waste including Water hyacinth (WH), cow manure (CM) and most of the organic wastes due to their organic compositions, they have a great potential for biogas production.

In this study Anaerobic Digestion technology (AD) a highly promising technology is used to convert Water hyacinth and Cow manure into biogas as a resource of energy.

Lab-scale experiments were carried out on some blends of fresh Cow manure collected from cow breeding farm and some of Water hyacinth harvested from Nile River.

Composition analyses of raw materials were carried out using Walkley and Black methods and Kjeldal method.

Lab-scale experiments were carried out to get the best conditions for producing the biogas.

All experiments on biogas productivity were conducted till the yield of biogas significantly decreased.

By using a feed stock of WH containing 30 g TS/L for 30 daysatconstant temperatures namely 25°C, 37°C and 45°C, it was found that the yield of biogas production yield at 37°C was more as compared to the other two temperatures 25°C, 45°C.

The biogas production yields at 25°C, 37°C and 45°C were 200 ml, 390 ml and 270 ml respectively.

For different Water hyacinth and Cow manure blends with different Carbon/ Nitrogen ratios (C/N) namely, (CN₂₀, CN₂₅, and CN₃₀) the experiments were conducted for 30 days at temperature 37°C.

The results showed that the yield of Biogas in descending order for CN₃₀, CN₂₅ and CN_20, were350 ml, 330 ml and 300 mlrespectively.

Also experiments showed that co-digestion is more productive for biogas production than mono-digestion.

Slurry of WH of 50 g TS/1 inoculated by CM with rate of 10% (v/v), the gas yield increased from 230 l/kg TS to 420 l/kg TS as compared to the uninoculated slurry at same conditions.

By charging the mobile digester by some blends of Water hyacinth and Cow manure (100% CM; 75% CM + 25% WH; 50% CM + 50% WH; 25% CM + 75% WH; and 100% WH) biogas were produced as results of treatment (122 L, 148 L, 176 L, 153 L, and 171 L respectively).

The contents of methane gas in biogas were between 50-60% .

The experiments results revealed that bio-organic materials could be potential sources for biogas production.

Using a mobile digester will have double advantages.

The first is generating biogas on site.

Second is disposal of biomass wastes.