Work experiences
July to  September, 2003, Field facilitator for mini-project for Master course on Livestock based Sustainable farming system (Livestock nutrition and growth performance, Nutrition value based on laboratory methods on plant leaves, recycling system of animal waste, and with horticulture)
May 2000 to July 2001 Farm Manager and Researcher worked for University of Tropical Agriculture Foundation (UTAF).
At present is working for regional biogas network project as project facilitator in riparian countries. And working part time with Cambodia Rural Development Team (CRDT) as technical advisor this project for rural development that developing on “Villager education associated with, and the installation of water and Bio-digester fuel supply at Takeo province” located in South eastern of Cambodia.

He is a researcher on an integrated biodigester in farming systems and has conducted research on management of biodigesters and utilization in integrated farming system, use of manure for charging tubular plastic biodigesters, by measuring on gas production and ammonia nitrogen. Effluent from biodigester was utilized to evaluate the fertilizer value by growing tilapia in small pond without supplementation. On this research line he is doing more detail on the dimension of biodigesters and different pig and cattle manure proportions, with  fish polyculture, and water plants.

Researches are beneficiary on reduce the bad impact on environment with an increasing the productivity and sustainable farming system.

In the first study, two experiments were carried out to determine gas production and fertilizer value of the effluent in plug-flow, tubular, plastic biodigesters with hydraulic retention times of 10, 20 or 30 days. There were three biodigesters each of 510 litres liquid volume in each experiment which consisted of three consecutive periods (retention times) of 40 days arranged in a 3*3 Latin Square. In experiment 1, the quantity of fresh pig manure was 5.1 kg/day, mixed with 46, 20 or 12 litres of water to give retention times of 10, 20 or 30 days, respectively.  In experiment 2, the proportions of pig manure and water were maintained constant to give a total solids content of 60 g/litre in the influent, which was added at rates of 51, 25.5 and 17 kg daily for retention times of 10, 20 or 30 days, respectively. Gas production was measured daily by water displacement in inverted lightweight containers (tubular polyethylene supported by bamboo strips) suspended in 200 litre drums filled with water. Influent and effluent were analyzed at weekly intervals for DM, OM, pH and total nitrogen and ammonia-nitrogen. Gas production was measured daily but only the data for the last 10 days of each period were used in the statistical analysis.

With a fixed daily input of fresh manure, neither the rate of gas production (1.04, 1.20 and 1.12 volumes of biogas per unit liquid volume of the biodigester) nor the efficiency (493, 606 and 567 litres of biogas/kg of manure organic matter added to the biodigester), were influenced by retention time (10, 20 or 30 days, respectively). However, when the solids concentration of the influent was fixed at 60 g/kg, rates of gas production were reduced by increasing retention times (1.62, 1.19 and 0.81 volumes biogas/unit liquid volume of biodigester for 10, 20 and 30 days retention); efficiency was better for 20 and 30 days retention (550 and 547 litres biogas/kg OM) than for 10 days (376 litres/kg OM). The proportion of ammonia-N in total-N increased from a range of 0.023 to 0.029 in the fresh manure to a range of 0.40 to 0.60 in the effluent and did not appear to be affected by retention time or loading rate.

It is concluded that when fresh pig manure is the substrate in polyethylene plug-flow biodigesters the optimum retention time is between 10 and 20 days with a solids concentration in the influent of 60 g/litre.  The retention time apparently has no effect on the degree of conversion of organic N to ammonia-N.

In the second study, the effluent from the experiment with constant solid concentration (60g/kg) were used for fertilizing tilapia ponds. A  randomized complete design  was used to study growth rate of Tilapia (Oreochromis niloticus) as influenced by pond fertilization (0.133g N/m2/day) with effluents from biodigesters having hydraulic retention time of 10 and 30 days. There were three replications (ponds of 6 m2 in area) of each treatment which was applied over a period of 120 days.

Growth rate and net fish yield were higher with effluent from 30 day retention time (0.43g/day and 1363 kg /ha) than with effluent from 10 day retention time (0.27g/day and 899 kg/ ha).  Mean values for BOD5 were higher for the 10 day retention time. 

It is concluded that the improved fish productivity with effluent from biodigesters with 30 day, compared with 10 day, retention times was probably due to a combination of lower BOD in the pond water, and a higher proportion of ammonia-N in the effluent. 
Keywords:  Biodigester, effluent, gas production, pig manure, fertilizer value, polyethylene, retention time, primary production, tilapia,  Oreochrmis niloticus,