Water remains as one of the major resources in rainfed lowland farming. A developed ricehull gasifier engine-pump system can use ricehull as source of alternative fuel for the prime mover to pump irrigation water for crop production. The system has 30 cm diameter reactor that uses an average 8.5 kg/hr fresh ricehull to supply producer gas to a 16 hp gasoline engine. Rainfall and shallow tube well (STW) are the sources of irrigation water identified for dry cropping season in the rainfed lowland farm. Groundwater, ranging from -1.7 m to -3 m water table depth is available for pumping during the whole cropping season with good recharging performance of 0.025 mms. Recharging period of the depleted groundwater after pumping operation was less than 2 hours.

Optimization scheme in using the developed gasifier system was established using three crops in a hectare farm (0.1 ha for onion, 0.8 ha for squash, and 0.1 ha for rice) to attain a maximum net benefits of P52,732.00 (potential). Based on the validation experiment using an actual area of 0.87 ha with clay loam soil, maximum economic benefits (P262,314.00) can be obtained using the areas of 2.5 ha, 0.2 ha, and 0.2 ha for onion, squash, and rice crops respectively, with optimum water drawn capacity of 186 m d. Economics of using the gasifier system for continuous pumping operation revealed that actual savings of P20,705.00 can be attained yearly with an investment payback period of 2.62 years and P1.23m pumping water cost.