Manufacturing technologies

The main technological thrust of first-generation biodiesel is transitioning (trans)esterification technology from traditional batch methodology to a continuous process in larger facilities. A considerable challenge for biodiesel is plant scale. Biomass collection makes the size of petrodiesel plants unattainable.

The right choice of technology provider in connection with the prospective feedstock use is also very important. Production technology should always lead to the same quality standard, independent of the oils or fats used. Highly flexible multi-feedstock use (including non-food high-energy oils) at the highest yield levels is a technological challenge. More systematic research is wanted on solid-catalyst activity for transesterification of TGs and esterification of FFAs with alcohols. More effective and cheaper manufacturing technologies are welcome; exchange of practical biodiesel experience is precious. Breakthroughs are needed for application of lipase catalysis to unrefined oils.

Table 16.2 illustrates the relation between biodiesel production and green chemistry principles. Biodiesel from vegetable oils is not a completely renewable product.

Table 16.2 Green chemistry and biodiesel production

Glycerol as by-product; wastewater; salt formation (fertilisers)

Low excess chemicals (recoverable)

Simple chemistry; low cost Potentially safe reagents and products; environmentally friendly (see Table 14.6); no VOCs; low toxicity

Toxic methanol; co-solvents; wastewater High T, p in non-catalytic processes Edible and non-edible vegetable oils and animal fats; used oils/fats Pre-treatment

Wide choice of catalysts and feedstocks; corrosiveness of some catalyst classes Diesel engine compatible product International standards; no hazardous substances

Inherently safe chemistry (low T, p) for accident prevention

While first-generation biofuels are essentially resource-based, the next generations will be mainly technology based. Renewable diesel fuel (e. g. HVO) is an emerging technological threat for first-generation biodiesel and could eventually seize a large slice of its market. Co-generation of biofuels is possible. A broader use of synthetic diesel will be possible if production processes are developed that are not based solely on oilseeds but on cheap and readily available renewable bulk plant materials such as sugars, starch, cellulosic and waste materials. Given their positive environmental assessment, biofuels from residues should be realised if technically and economically viable. Biomass is expected to contribute significantly to renewable energy but at present the efficiency of integral biomass conversion is very limited and technologies are still evolving. Next-generation renewable diesel from biomass cellulose requires at least another decade before full commercialisation. Oleaginous biomass-based renewable fuel production may profitably be integrated in a refinery environment. In the medium to long term, BTL fuel production will become more attractive than biodiesel from (non)edible vegetable oil sources.

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