Author : May Soe Oo

Summary : Two studies were conducted almost simultaneously to determine the energy bills, energy use indicators, and energy footprints of two rice genotypes grown under organic and conventional systems from production to cooking stages. Study 1 was conducted from November 2016 to March 2017 in Bay, Laguna. Grown under organic system, the field experiment was laid out in strip plot wherein the main plots were the three spacings (20 x 20 cm, double rows, and 30 x 30 cm) and the subplots were the five rice varieties (Pbinhi-1, Bigante, GSR-8, M-20, and Rc-222). For comparison, a farmer-based system (Study 2) was conducted from December 2016 to April 2017 in the same town.

The organic system at 5,858 MJ ha-1 reduced the total energy bill by as much as 81 percent when compared with the conventional system that used a total of 30,469 MJ ha-1. The major energy hotspots for the conventional system were agrochemical inputs particularly nitrogen fertilizer at 20,015 MJ ha-1 (66%) and pesticides at 2,486 MJ ha-1 1 (8%). The major energy inputs for the organic system were organic fertilizer at 1,440 MJ ha-1 (25%) and labor at 1,134 MJ ha-1 1 (20%). The energy output was lower in the organic system at 84,180 MJ ha-1 and higher in the conventional system at 113,998 MJ ha-1 due mainly to higher yields at 6,806 kg ha-1 in the conventional system compared to 5,026 kg ha-1 1 in the organic system. The lower energy bill in the organic system led to a much lower energy needed to produce one kg of unmilled rice at 1.19 MJ kg-1, while it was 4.46 MJ kg-1 in the conventional system.

Also, the energy returns over energy inputs (EROEI) and energy productivity values were higher in the organic system (15 and 0.87 kg MJ-1) and much lower in the conventional system (4 and 0.223 kg MJ-1). Furthermore, about 1,819 kg ha-1 of unmilled rice was needed to produce to break even the total energy inputs in the conventional system, while it was only 350 kg ha 1 unmilled rice needed in the organic system.

Post-production and cooking stages added significant amounts of energy to the overall energy bill, reaching 8,816 MJ ha-1 in the organic system and 34,336 MJ ha-1 in the conventional system. In turn, the energy use per ton of milled rice increased at 1,771 MJ/ton in the organic system and 5,096 MJ/ton in the conventional system. Transport accrued the highest energy use per ton of milled rice in post-production (18%–55% more) when rice is transported over long distances of 200 km and above.

The energy footprint of hybrid rice per hectare was only 147 kg CO2 e/ton in the organic system, while it was 422 kg CO2 e/ton in the conventional system, which was 2.8 times higher. The implication of the findings is that the organic production system reduces the fossil fuel needed and thus reduces the energy bill and energy footprint (CO2 emission) in rice by as much as three times.