Co-composting of palm oil mill wastes.

Co-composting is one of the important bio-waste treatments in the palm oil industry for achieving sustainable process and zero waste. However, improper conditions of composting may cause several problems such as gas emission, bad odour, low quality product, production delay and high handling cost. Enhancing the efficiency of waste composting becomes a vital issue to overcome these problems. This review provides information on the practices and developments related to co-composting of the palm oil mill waste. The description on a typical palm oil mill process and the wastes generated, i.e. empty fruit bunch and palm oil mill effluent, as composting substrates are given. The common windrow composting system is described. The recent venture of using microorganisms in composting processes are also covered under the pretext of several researchers’ interpretation that composting can be accelerated by the introduction of microorganism to the process through its influence on the physical, dynamic and biological behaviours of organic material. The criteria of choosing functional microbes for fast composting are discussed

Acceleration effects of microbial inoculum on palm oil mill organic waste composting.

ABSTRACT The acceleration effects of inoculum in composting of empty fruit bunches were investigated. Composting of empty fruit bunches fibres in two sizes, 4 cm and 2 cm length, were treated with microbial inoculum consisting of Agromonas, Aspergillus, Azotobacter, Bacillus, Celhdomonas, Chaetomium, Clostridium, Coprinus, Microbispora, Penicillium, Pseudomonas, Thermoactinomyces, Trichoderma and Trichurus in separate laboratory scale in-vessel of 30 liters volume. A control without inoculum with 4 cm length empty fruit bunches was also conducted in parallel. The compost piles were shift-turned weekly. Parameters such as moisture content, temperature, pH, and electrical conductivity were used to monitor the composting processes. The carbon-nitrogen ratio, UV-vis spectrophotometer test, and germination test were used to assess the maturity of compost. The results showed that the inoculum was effective in reducing the C/N ratio by 54% compared to control 46% and rapidly increasing the UV-vis absorption ratio in first three weeks. By using functional microbes, the composting of empty fruit bunches was reduced to 5 weeks compared to 9 weeks for those without inoculation. The acceleration effect was more prominent for the 2 cm length samples

Composting of empty fruit bunches by microbial inocular

The increment of palm oil production increases its by-product wastes such as the empty fruit bunch (EFB) and palm oil mill effluent (POME). To recycle the wastes,large-scale windrow composting system is established. However, the duration of compost production from two months to one-year is not compatible to the daily output of the palm oil mill wastes. Thus, accelerating of EFB composting by using inoculums, urea and a smaller substrate size were investigated. Parameters such as moisture content, temperature, pH, electrical conductivity and turning frequency were used to monitor the composting process of EFB and POME. The carbonnitrogen ratio, UV-vis spectrophotometer test, microorganisms enumeration and germination test were used to assess the maturity of compost. Two pilot scale tests were conducted in an industrial compost plant. The first pilot scale test aims to verify the effectiveness of inoculums and urea addition in 30 tonne of EFB compost piles. Four heaps of EFB with different treatments i.e. addition of 0.03%, 0.3% of commercial inocular, 200 kg urea, and control without any additives were investigated. The result disclosed that the 0.03% of inocular had positively affected the composting performance by decreasing the C/N ratio to 15.04 compared to the control, which had the final C/N of 21.39. The EFB heap with addition of urea also had its C/N decreased to 15.62, thus urea may be a second option for accelerating the composting process. In the second pilot scale trial, four heaps of composts were used. Daily turning was done on a heap containing commercial inocular, a heap added with laboratory inocular consisting 15 types of func ional microbes and the control heap. Another heap with the aboratory inocular was scheduled turning once in every two da ys. This trial revealed that the moisture loss and degradation rate were not significantly different between composts with different turning frequencies. With similar decreasing rate of the C/N ratio and microbes population, the laboratory and commercial inoculars were found similar in assisting composting. Both the inoculars have an enhancing effect on the EFB composting as the C/N of both inoculated composts dropped below 20 at 14 days earlier than control. In the third trial, three composts of 20 kg of EFB each were evaluated for the time efficiency of laboratory inocular in smaller particle size of substrate. Composts with 4 cm and 2 cm particle sizes of EFB were inoculated, and a control with 4 cm fibres was without inocular. The C/N of inoculated composts with 2 cm fibres dropped to 18.31, whereas the control was 20.65. The UV-vis ratio of the 2 cm fibre became constant earlier than the control by at least 3 weeks. Observations on the germination test and microbe enumeration suggested that 2 cm inoculated compost matured earlier, i.e. in 35 days compared to the 4 cm fibre at 49 days and the control not mature even at 60 days. In conclusion, the laboratory inoculars can be useful in speeding up the composting process of EFB, particularly for those with smaller substrate sizes. (499