Emerson’s Meha Jha presented Renewable Diesel 101 for HSE Personnel at the 2022 4C HSE conference. She opened with an overview of the biofuels market. Regulatory Initiatives globally encourage using alternative fuel sources that are cleaner burning versus traditional petroleum-based fuels.
Biofuels compete directly with petroleum-based products, including gasoline and diesel, increasingly with new technologies including electric, compressed natural gas, fuel cells, etc. Currently, the three main types of biofuels are ethanol, biodiesel, and green diesel/renewable diesel. Also, sustainable aviation fuel (SAF) is emerging.
Meha described the types of diesel. Traditional petroleum diesel is produced by oil refineries in the distillation, catalytic cracking, and hydrotreating processes. Biodiesel is made in a transesterification process where biomass (animal fats, corn oil, recycled cooking & vegetable oil) is reacted with methanol to produce fatty acid methyl esters (FAME).
Green diesel, known as renewable diesel, is the 2nd generation of renewable diesel. The feedstock is biomass, but hydrotreating and isomerization of triglycerides are performed—similar to refining processes—which eliminates oxygen in the conversion process. It does not require blending with petroleum-based diesel as a transportation fuel. Only economic subsidies now make green diesel production competitive with traditional diesel production.
Meha explained how California is driving demand for biodiesel with economic incentives. Other states such as Oregon and Washington and the Canadian province of British Columbia are following California’s lead. One of the biggest drivers for refiners is economics. There is currently a 33% rate of return estimated for these biodiesel production investments, supported by the regulatory environment. These regulations also allow refiners to diversify away from the fossil fuel-based refining economics while adding independence to the price of crude oil and the cracking margins.
Minimizing the feedstocks’ carbon intensity (CI) maximizes the regulatory credits. Everything from where the farm is located to how the feedstock is transported is part of the calculation. Waste products, like tallow oil or used cooking oil, would be the most advantaged. Carbon intensity is how much carbon dioxide (CO2) or carbon dioxide equivalent (CO2-e) is emitted by the complete lifecycle of a fuel per unit of energy delivered. The lower the CI Score, the higher the credit.
For biodiesel production, there are three main sections of the plant. The feedstocks to the plant have to be pretreated before they can be processed, so there is usually a pre-treatment area. In some plants, this pretreatment is done at another facility. The green diesel producer will purchase pretreated feed, but this is somewhat restrictive, so most operators plan to build a pretreatment plant if they don’t already have one. The pretreatment area’s function is to protect the downstream catalyst since the feedstocks contain contaminants that will poison the catalyst in the reactors.
From the pretreatment area, the feed enters the deoxygenation reactor, which uses hydrogen to remove oxygen from the feedstocks, creating hydrocarbons similar to fossil-based diesel. A second reactor is an isomerization unit that adjusts the cold flow properties of the product. The process produces light ends and naphtha, but primarily diesel fuel. There is also typically an offsites section of these projects where the new feedstocks and products are unloaded, loaded, and stored, or the products are sent to a terminal.
Some of the measurement technologies used in the reactor process include:
Visit the Renewable Biofuels Production section on Emerson.com for more ways to drive more sustainable operations in your production process.