feedstock such as ethylene and propylene can also be produced directly by cracking crude oil. Oil refineries are therefore typically large industrial complexes with chemical processing units, such as fractional distillation columns, and use much of the technology as in chemical plants.
Figure 1. A biorefinery is generally defined as a renewable mirror of a petroleum refinery.
Figure 2. Various plant materials, collectively known as biomass, are a potential feedstock to produce substitutes for petroleum-derived fuels and building blocks for biochemicals.
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ENERGY GLOBAL SUMMER 2022
Replacing fossil fuels with biofuels Fuels produced from renewable organic material have the potential to reduce dependence on unstable foreign suppliers and lower some of the undesirable aspects of fossil fuel production and use, including greenhouse gas (GHG) emissions, the depletion of non-renewable fossil fuel resources, and geopolitical dependencies. Demand for biofuels could also increase farm income by utilising locally grown renewable feedstocks. Analogous to petrorefining, the concept of biorefining is emerging. A biorefinery is generally defined as a renewable mirror of a petroleum refinery, where a variety of fuels, chemicals, and power are produced from one source. The characteristics of the modern biorefinery are parallel to the petroleum refinery: an abundant raw material, consisting primarily of renewable biomass, enters the biorefinery and is converted into fuels, biochemicals, and direct energy. While there are similarities between the biorefinery and the petroleum refinery, there are also important differences. For example, there is more oxygen present in bio-based chemicals, which leads to opportunities for production of certain organic products. Separations are as critical for the biorefinery as they are for the petroleum refinery. Bioprocess separations costs can account for up to 50 - 70% of processing costs. Various plant materials, collectively known as biomass, are a potential feedstock to produce substitutes for petroleum-derived fuels and building blocks for biochemicals. Biomass is abundant and currently is still low in utilisation. Unlike other renewable energy sources, biomass can be converted directly into liquid fuels, called biofuels, to help meet transportation fuel needs. The two most common types of biofuels in use today are ethanol and biodiesel, both of which represent the first generation of biofuel technology. Ethanol is a renewable fuel being produced from biomass. Ethanol is used as a blend with gasoline to increase octane, and reduce carbon monoxide and other emissions. The most common blend of ethanol is E10 (10% ethanol, 90% gasoline) and is approved for use in conventional gasoline-powered vehicles. Furthermore, ethanol can be used as an intermediate for the production of green polyethylene and esters. The vast majority of ethanol is currently made from plant starches and sugars; particularly corn starch in the US, but technologies are being developed and enhanced that would allow for the use of cellulose and hemicellulose, the non-edible fibrous material that constitutes the bulk of plant matter. Biodiesel is a renewable, biodegradable, cleaner burning fuel manufactured from an increasingly diverse mix of feedstocks, such as various vegetable oils, waste animal fats, or recycled cooking oil. Biodiesel is a liquid fuel often referred to as B100 or neat biodiesel in its pure, unblended form. B100 biodiesel can be directly used in existing diesel engines or can be blended with regular diesel, such as B5 and B20, for use in colder climate areas. Biodiesel is made through a chemical process called transesterification whereby the glycerin is separated from the fat or vegetable oil. Currently, ethanol and biodiesel plants are mostly standalone facilities near their feedstock plantations. The biorefinery is still lacking in competitiveness compared to a
