<b>Analyses of energy use and greenhouse gas emissions in rice production under acidic soil conditions in Malaysia</b>

Fuel energy</b></p></td></tr></table><p dir="ltr">Fuel energy is calculated based on the type (diesel or gasoline) and quantity of fuel consumed in performing various operations of farming, multiplied by the energy conversion for fuel. The general calculation is given in Eq. (S2).</p><table><tr><td><table><tr><td><p dir="ltr">(EAEF190208_eq_S2.png)</p></td></tr></table></td></tr></table><p dir="ltr">Where EF is the fuel energy (MJ/ha), <i>Fq</i> is the quantity of consumed fuel (L), <i>Fc</i> is the energy conversion factor for fuel (MJ/L), and <i>A</i> is the field area (ha).</p><p dir="ltr"><b>1.3.

Seed energy</b></p><p dir="ltr">Seed energy was estimated by multiplying the quantity of seed per unit area by its energy conversion factor. The general calculation is presented in Eq. (S3).</p><table><tr><td><table><tr><td><p dir="ltr">(EAEF190208_eq_S3.png)</p></td></tr></table></td></tr></table><p dir="ltr">Where the ES is the seed energy (MJ/ha), <i>Sq</i><i> </i>is the quantity of seed used (kg), <i>Sc</i> is the energy conversion factor for seed (MJ/kg), and <i>A</i> is the field area (ha).</p><p dir="ltr"><b>1.4.

Lime energy</b></p><p dir="ltr">Lime energy was estimated based on the quantity of Ground Magnesium Limestone (GML) applied per unit area multiplied by the energy conversion factor for limestone adopted from Guareschi et al. (2020, 2021). The general calculation is presented in Eq. (S4).</p><table><tr><td><table><tr><td><p dir="ltr">(EAEF190208_eq_S4.png)</p></td></tr></table></td></tr></table><p dir="ltr">Where ELi<i> </i>is the lime energy (MJ/ha), <i>Liq</i> is the quantity of lime used (kg), <i>Lic</i> is the energy conversion factor for lime (MJ/kg), and <i>A</i> is the field area (ha).</p><p dir="ltr"><b>1.5.

Fertilizer energy</b></p><p dir="ltr">The energy embodied in chemical fertilizer is estimated based on the quantity of fertilizer used per unit area (kg/ha) and the percentage of the fertilizer composition multiplied by the energy conversion factor for fertilizer (nitrogen, phosphate, potassium). The general calculation is presented in Eq. (S5).</p><table><tr><td><table><tr><td><p dir="ltr">(EAEF190208_eq_S5.png)</p></td></tr></table></td></tr></table><p dir="ltr">Where EFT is the fertilizer energy (MJ/ha), <i>FTq</i> is the quantity of fertilizer used (kg), <i>n</i> is the total number of fertilizer components, <i>FT</i>_<em>i</em> is the percentage of fertilizer composition used, <i>FTc</i>_<em>i</em> is the energy conversion factor for fertilizer (MJ/kg), and <i>A</i> is the field area (ha).</p><p dir="ltr"><b>1.6.

Agrochemical pesticides energy</b></p><p dir="ltr">Pesticides energy was estimated based on the quantity of pesticides used per unit area and the percentage of the active ingredient composition multiplied by the energy conversion factor for pesticides (insecticides, pesticides, herbicides, molluscicides, and rodenticides). The general calculation is presented in Eq. (S6).</p><table><tr><td><table><tr><td><p dir="ltr">(EAEF190208_eq_S6.png)</p></td></tr></table></td></tr></table><p dir="ltr">Where EP is the pesticides energy (MJ/ha), <i>Pq</i> is the quantity of pesticides used (kg), <i>n</i> is the total number of pesticides components, <i>P</i>_<em>i</em> is the percentage of active ingredient in pesticides used, <i>Pc</i>_<em>i</em> is the energy conversion factor for pesticides (MJ/kg), and <i>A</i> is the field area (ha).</p><p dir="ltr"><b>1.7.

Labour energy</b></p><p dir="ltr">Labor energy was evaluated based on the number of workers involved in the operation per unit area and working time in the operation multiplied by the energy conversion factor for labor. The general calculation is presented in Eq. (S7).</p><table><tr><td><table><tr><td><p dir="ltr">(EAEF190208_eq_S7.png)</p></td></tr></table><p dir="ltr"><br></p></td></tr></table><p dir="ltr">Where EL is the labor energy (MJ/ha), <i>n</i> is the number of workers involved in operations, <i>H</i> is the working time (h), <i>Lc</i> is the energy conversion factor for labor (MJ/h), and <i>A</i> is the field area (ha).</p><p dir="ltr"><b>1.8.

Total energy input</b></p><p dir="ltr">Total energy used in rice farming per hectare is determined as the summation of energy from all sources. The general calculation is presented in Eq. (S8).</p><table><tr><td><table><tr><td><p dir="ltr">(EAEF190208_eq_S8.png)</p></td></tr></table></td></tr></table><p dir="ltr">Where TEI is the total energy input (MJ/ha), and EM, EF, ES, ELi, EFT, EP, and EL as defined above.</p><p dir="ltr"><b>2.

GHG emissions analysis</b></p><p dir="ltr">This study was focused on GHG emission (kgCO₂-eq/unit)<i> </i>emitted from farm input such as machinery, fossil fuels, chemical fertilizers, and agrochemicals. The amount of GHG emission was obtained the farm input by its emission coefficient using Eq. (S9–16) as follow.</p><p><br></p><p dir="ltr"><b>2.1.

Machinery emission</b></p><p dir="ltr">Machinery emissions were estimated by machinery energy use per unit area multiplied by the emission factor for machinery. The general calculation is presented in Eq. (S9).</p><table><tr><td><table><tr><td><p dir="ltr">(EAEF190208_eq_S9.png)</p></td></tr></table></td></tr></table><p dir="ltr">Where CM is the CO₂ emissions from machinery (kg CO₂-eq/ha), <i>Mq</i> is the quantity of machinery energy (MJ), <i>Me</i> is the emission factor for machinery (kg CO₂-eq/MJ), and <i>A</i> is the field area (ha).</p><p><br></p><p dir="ltr"><b>2.2.

Fuel emissions</b></p><p dir="ltr">Fuel combustion emissions were evaluated based on the quantity of fuel consumed per unit area multiplied by the emission factor for each fuel type (diesel/gasoline). The general calculation is presented in Eq. (S10).</p><table><tr><td><table><tr><td><p dir="ltr">(EAEF190208_eq_S10.png)</p></td></tr></table></td></tr></table><p dir="ltr">Where CF is the CO₂ emissions from fuel (kg CO₂-eq/ha), <i>Fq</i> is the quantity of fuel consumed (L), <i>Ee</i> is the emission factor for fuel (kg CO₂-eq/L), and <i>A</i> is the field area (ha).</p><p dir="ltr"><b>2.3.

Seed emissions</b></p><p dir="ltr">Seed emissions were estimated based on the quantity of seed per unit area multiplied by the emission factor of seed. An emission factor of 1.5 kg CO₂-eq./kg rice seed was calculated based on data reported by Rahman et al. (2019). The general calculation is presented in Eq.

(S11).</p><table><tr><td><table><tr><td><p dir="ltr">(EAEF190208_eq_S11.png)</p></td></tr></table></td></tr></table><p dir="ltr">Where the CS is the CO₂ emission from seed (kg CO₂-eq/ha), <i>Sq</i> is the quantity of seed used (kg), <i>Se</i> is the emission factor for seed (kg CO₂-eq/kg), and <i>A</i> is the field area (ha).</p><p dir="ltr"><b>2.4. Lime emissions</b></p><p dir="ltr">Lime emissions were estimated based on the quantity of lime used per unit area multiplied by the emission factor for lime.

The general calculation is presented in Eq. (S12).</p><table><tr><td><table><tr><td><p dir="ltr">(EAEF190208_eq_S12.png)</p></td></tr></table></td></tr></table><p dir="ltr">Where CLi is the CO₂emissions from lime (kg CO₂-eq/ha), <i>Liq</i> is the quantity of lime used (kg), <i>Lie</i> is the emission factor for lime (kg CO₂-eq/kg), and <i>A</i> is the field area (ha).</p><p dir="ltr"><b>2.5.

Fertilizer emissions</b></p><p dir="ltr">Fertilizer emissions were estimated based on the amount of chemical fertilizer usage per area multiplied by the emission factor for fertilizer. The general calculation is presented in Eq. (S13).</p><table><tr><td><table><tr><td><p dir="ltr">(EAEF190208_eq_S13.png)</p></td></tr></table></td></tr></table><p dir="ltr">Where CFT is the CO₂ emissions from fertilizer (kg CO₂-eq/ha),<i> </i><i>FTq</i> is the quantity of fertilizer used (kg), <i>n</i> is the total number of nutrient components<i>,</i><i> </i><i>FT</i>_<em>i</em> is the percentage of fertilizer composition used<i>, FTe</i>_<em>i</em> is the emission factor for chemical fertilizer (kg CO₂-eq/kg), and <i>A</i> is the field area (ha).</p><p dir="ltr"><b>2.6.

Pesticide emissions</b></p><p dir="ltr">The pesticides emissions were specified into insecticides, herbicides, fungicides, molluscicides, and rodenticides. However, due to the lack of information about GHG emissions related to the molluscicides and rodenticides, a general emission factor of 25.5 kg CO₂ equivalent per kg of active ingredient was used, as referred to in the formula by Audsley et al. (2009).</p><table><tr><td><table><tr><td><p dir="ltr">(EAEF190208_eq_S14.png)</p></td></tr></table></td></tr></table><p dir="ltr">Where EGH is the CO₂ emissions from pesticide (kg CO₂-eq/ha), <i>Aa</i>_<em>i</em> is the amount of active ingredient of pesticide applied (kg/ha), and <i>CF</i> is the emission factor for pesticide.</p><p dir="ltr"><b>2.7.

Labor emissions</b></p><p dir="ltr">The labor emissions were evaluated based on the number of workers involved in the operation per unit area and working time in the operation multiplied by theemission factor for labor. The general calculation is presented in Eq. (S15).</p><table><tr><td><table><tr><td><p dir="ltr">(EAEF190208_eq_S15.png)</p></td></tr></table></td></tr></table><p dir="ltr">Where CL is the CO₂ emissions from labor (kg CO₂-eq/ha), <i>Lq</i> is the quantity of labor, <i>Le</i> is the emission factor for labor (kg CO₂-eq/h), and <i>A</i> is the field area (ha).</p><p dir="ltr"><b>2.8.

Total emissions</b></p><p dir="ltr">Total GHG emissions of rice farming per hectare are determined as a total the summation of CO₂ emissions based on the system boundary. The general calculation is presented in Eq. (S16).</p><table><tr><td><table><tr><td><p dir="ltr">(EAEF190208_eq_S16.png)</p></td></tr></table></td></tr></table><p dir="ltr">Where TEC is the total emission (kg CO₂-eq/ha) and CM, CF, CS, CLi, CFT, EGH and CL as defined above.</p><p dir="ltr"><b>References</b></p><p dir="ltr">Audsley, E. et al. 2009.

Estimation of the greenhouse gas emissions from agricultural pesticide manufacture and use. Cranfield University.</p><p dir="ltr">Guareschi, R. F. et al. 2020. Energy use efficiency in soybean crops in different regions of Brazil.

Semina: Ciências Agrárias. 41 (6Supl2): 2991–3010. doi.org/10.5433/1679-0359.2020v41n6Supl2p2991</p><p dir="ltr">Guareschi, R. F. et al. 2021. Energy efficiency in maize crops in different regions of Brazil. Semina: Ciências Agrárias. 42 (4): 2271–2292. doi.org/10.5433/1679-0359.2021v42n4p2271</p><p dir="ltr">Muazu, A. et al. 2015.

Machinery utilization and production cost of paddy cultivation under wetland direct seeding conditions in Malaysia. Engineering in Agriculture, Environment and Food. 8 (4): 289–297. doi.org/10.1016/j.eaef.2015.03.007</p><p dir="ltr">Rahman, M. H. A. et al. 2019. Life cycle assessment in conventional rice farming system: estimation of greenhouse gas emissions using cradle-to-gate approach.

Journal of Cleaner Production. 212: 1526–1535. doi.org/10.1016/j.jclepro.2018.12.062</p>