Examining the data originality of the publications shows that Technologies & Residue Use publications are largely based on primary data, whereas Socio-economic and Emissions & Impacts research have generally made use of secondary data (see Fig. 4). One may have expected to see a large portion of primary data under the Emissions & Impacts category. This is partially explained by emissions data related to LULUC and Technologies & Residue Use being included in those specific categories and not in the Emissions & Impacts category. For the most part, research under the Emissions & Impacts is life TNKS 22 assessment (LCA) related and primary data generation is seldom practiced in LCA.
3.2. Technologies & Residue Use
Residues from palm oil production include fronds and oil palm trunks from the plantations and empty fruit bunches, palm press fibre, palm kernel shells, boiler ash and POME from the palm oil mills.
The increase in Technologies & Residue Use publications follow an exponential trend from just 8 publications in 2004 to 109 publications in 2013 (see Fig. 7). Furthermore, Fig. 7 shows that whereas the treatment and use of the residues are by default related to sustainability, only a small fraction (3%) of the studies quantify or discuss the environmental emissions and/or benefits of the treatment. The vast majority of the residue studies focus solely on the technical feasibility of technologies or the characteristics of the products produced from the residues. Research on residue uses, and in particular the technical feasibility of technologies is conducted mainly in palm oil producing countries in Southeast Asia.