Abstract : Palm oil systems generate large amounts of biomass residues. According to best agri-cultural practices, they are supposed to be returned back to plantation to maintain soil fertility. However, there are variations in practice. Differences in economic status and treatment options on biomass residues cause variations on the preference to perform LCA, leading to divergence in results that complicate interpretation. Difficulties found in comparing LCA results based on literature are not unusual. The objective of the paper is to provide guidelines on methodological choices to systematically compare diverse scenarios on the treatment and valuation of EFB (Empty Fruit Bunches) and to explore their effects on the environmental performances of a palm oil system.
Eleven scenarios were chosen to cover possible EFB valuation and expanded system boundaries with reference to the main palm oil system (application as mulch, conversion to compost or ethanol, treatment in an incinerator, and EFB as direct co-products). The life cycle inventories were modeled based on Ecoinvent database. The input EFB was considered either as wastes or goods, and the resulted products were used internally or externally. Solution to multi-functional problems was suggested, including the application of system expansion, substitution, and partitioning depending on the nature of the scenario.
The contribution of the plantation phases on global warming impact was so dominant that the effect of different scenarios could be observed only when focusing on the oil mill stage. Comparison among LCA results based on the same multi-functional units (crude palm oil + palm kernel oil + palm kernel cake) can be done only in the cases where additional co-products (mulch, compost, or ethanol) were used internally. Based on global warming impact, the mulch option was the best choice as compared to the compost, ethanol, or incineration options. The effect of the avoided process of producing substituted fertilizers was dominant in this comparison result. This study also demonstrates that the status of EFB as wastes or goods is influential to the final results when the EFB is used externally, but has no effect when it is used internally.
The proposed guidelines provide methodological choices in terms of system boundary, functional unit, and solution to multi-functional problems. The methods can be used to systematically compare LCA results of different treatment options and valuation of EFB. The best alternative in handling biomass residues could improve environmental performances of the palm oil system and orient towards best practices, such as those suggested by the Roundtable on Sustainable Palm Oil. Further studies using a specific case of palm oil systems would better illustrate the usefulness of the proposed guidelines. Although the approach was illustrated for a palm oil system, it is also readily applicable for handling biomass residues in other agro-based industrial systems.