The Renewable Fuel Standard, or RFS, is a U.S. federal program designed to increase the amount of renewable fuel in the nation's transportation fuel supply. Think of it as a recipe for the country's fuel mix, where the government requires a certain percentage to come from sources like corn, soybeans, or other biomass instead of just crude oil.

Why do this? The program has three main objectives. First, it aims to reduce greenhouse gas emissions from transportation, a major contributor to climate change. Second, it's meant to decrease American dependence on imported oil, enhancing national energy security. Finally, it supports the domestic agricultural sector by creating a large market for crops that can be turned into fuel.

The RFS didn't appear overnight. It began with the Energy Policy Act of 2005. This initial version set the first-ever renewable fuel volume targets for the nation.

Just two years later, the Energy Independence and Security Act of 2007 (EISA) significantly expanded the program. EISA raised the volume requirements for renewable fuels, extending them out to 2022. It also established specific categories for these fuels, each with its own greenhouse gas reduction thresholds.

Several groups are involved in making the RFS work. At the top is the U.S. Environmental Protection Agency (EPA). The EPA is the referee, responsible for setting the annual renewable fuel volume requirements and ensuring everyone follows the rules.

Next are the "obligated parties." These are the oil refiners and gasoline and diesel importers. The RFS legally requires them to blend renewable fuels into their products. They are the ones who must meet the annual quotas set by the EPA.

Finally, there are the renewable fuel manufacturers. These are the companies that produce the actual biofuels, such as ethanol from corn or biodiesel from soybean oil. They are the source of the renewable products that obligated parties need to meet their requirements.

Not all renewable fuels are treated the same under the RFS. The program divides them into four main categories, each with specific requirements for feedstock and greenhouse gas (GHG) reduction compared to traditional petroleum fuels.

These categories create a tiered system. The law requires specific volumes for each, pushing the industry toward developing fuels that offer greater environmental benefits. The higher the GHG reduction, the more "advanced" the fuel is considered within the RFS framework.

Understanding these fundamentals—the what, why, who, and which fuels—is the first step to grasping how this complex but important environmental policy works.