“Clean” diesel oils and biofuels

“Clean” diesel oils and biofuels

There are existing and emerging diesel alternatives that do originate from mineral petroleum sources. This class of liquid fuels especially includes sustainable biofuels, sometimes called “green diesel” or “drop in biodiesel”. These are oils produced from land-grown plant biomass or water-grown lipid forming algae. Bioethanol and biomethane are further biofuels. All of these when combusted release carbon dioxide, but some supply chains can be engineered to offset Scope 1 emissions with off-site upstream credits. The fuels may be sustainable because they originate from biological processes. A related category includes “e-diesel” oils chemically synthesised from existing CO2 off gas sources that may be natural or industrial.

The United States Department of Energy’s Office of Energy Efficiency and Renewable Energy (EERE) operates an Alternative Fuels Data Center (AFDC) with a good general overview of renewable hydrocarbon research.1 These fuels are short- term or medium-term alternatives for internal combustion engine vehicles, especially large marine engines and ultra-heavy trucks, and aviation fuels. Incumbent petroleum suppliers, engine manufacturers and machinery OEMs are especially active in this space.

In Europe, Sunfire of Germany is producing an “e-diesel” product.2 Sunfire performs water electrolysis, reacts the hydrogen with CO2, and performs Fischer-Tropsch chemistry to make synthetic, non-biological diesel that is overall neutral or negative carbon because the overall supply chain consumes CO2. Norsk e-fuel will begin construction of a plant in 2023 that includes direct air capture of CO2 and water electrolysis.3 Audi built a 2017 plant in Switzerland that supplied a small volume of e-diesel.4

Costs and timelines have been estimated by Boston Consulting Group.5 Sustainable biodiesel is available now, at about double the cost of mineral petroleum diesel. BCG predicts that e-diesel will be more available by 2030.

Specific off-the-shelf solutions include initiatives from Exxon6 and Royal Dutch Shell.7 Rio Tinto announced8 a one year trial for marine diesel with BP which includes fatty acid methyl esters (FAME) from spent cooking oil that will be tested on the company’s Tasman vessel which ships iron ore from Australia.9

Although biodiesels and e-diesels are emerging as suitable for mining application, these solutions will not address related underground mining challenges related to ventilation of combustion by-product gas accumulation and fine particulate matter. The challenges of ventilation, heat, and underground air quality would persist.