What Is Bioheat? The Biodiesel Blend in Your Heating Oil (And Why It Matters)

If you heat your Connecticut home with oil, you're almost certainly burning Bioheat — whether you know it or not. Connecticut became one of the first states to mandate a minimum biodiesel blend in heating fuel, and most dealers in the Northeast have been delivering blended fuel for years. Here's what it actually is and what you need to know.

What Is Bioheat?

Bioheat is heating oil blended with a percentage of biodiesel — a renewable fuel derived primarily from soybean oil, recycled cooking grease, animal fats, or other biological feedstocks. The "B" number indicates the biodiesel percentage: B5 means 5% biodiesel, 95% petroleum heating oil; B20 means 20% biodiesel; B100 is pure biodiesel.

Connecticut requires a minimum B5 blend (at least 5% biodiesel) in residential heating fuel. Several other Northeastern states have similar or higher mandates. Rhode Island requires B5, New York City requires B20 in commercial buildings, and the trend across the region is toward higher blend requirements over time.

The fuel that comes out of your delivery truck looks identical to conventional heating oil. It burns in the same equipment, through the same nozzles, without any modification required. For most homeowners, nothing is different — you just happen to be burning a greener product.

Why Is Biodiesel Added to Heating Oil?

Several reasons, depending on who you ask:

Environmental mandate: Biodiesel combustion produces less carbon dioxide than petroleum-based heating oil on a lifecycle basis (the plants used to produce it absorbed CO2 while growing). B5 reduces carbon emissions roughly 3-5% compared to straight petroleum oil. B20 reduces them by 15-20%. States with greenhouse gas reduction goals use biofuel mandates as one tool toward those targets.

Lubricity improvement: Biodiesel has natural lubricating properties that reduce wear on fuel pump components and burner nozzles. Many oil industry professionals report that B5–B20 blends actually extend burner nozzle life compared to straight petroleum oil. This is a genuine practical benefit, not just marketing.

Energy security: Domestically produced biodiesel reduces reliance on petroleum imports. Soybean oil, recycled restaurant grease, and tallow are all domestic sources.

Does Bioheat Affect My Furnace or Boiler?

For B5 and B20 blends: no. All modern oil heating equipment is fully compatible with up to B20. The National Oilheat Research Alliance (NORA) and equipment manufacturers have tested and certified compatibility up to B20 for equipment manufactured since the early 2000s. No modifications are required, no adjustments to burner settings, no changes to your service schedule.

Higher blends (B50 and above) require verification of equipment compatibility, particularly for older systems. The rubber gaskets and seals in some older burners can degrade with high biodiesel concentrations. If your furnace or boiler is older than 20 years, ask your service technician about compatibility before switching to a high-blend supplier.

The Trajectory: Higher Blends Are Coming

Connecticut's B5 requirement is a floor, not a ceiling. The oil heat industry's Bioheat roadmap targets B50+ blends by 2030 in the Northeast as part of a pathway toward carbon-neutral heating. Several CT dealers are already voluntarily delivering B20 or higher to customers who request it.

This matters because it changes the long-term outlook for heating oil as a fuel. A home heating on B50 in 2030 has roughly half the carbon intensity of a petroleum-only system — competitive with natural gas from a emissions standpoint, and potentially lower with higher blends. The oil industry's argument to regulators and homeowners: you don't need to rip out your oil system to reduce emissions; you can transition the fuel blend while keeping the equipment.

Can I Request a Higher Bioheat Blend?

Yes. A growing number of CT dealers offer B20 or higher at a modest premium (typically $0.05-$0.15/gallon over B5 pricing). If reducing your carbon footprint is a goal and you want to act without converting your system, asking your dealer for a higher-blend product is a straightforward option.

Some dealers are beginning to market B20 or B50 as a premium product under the Bioheat+ branding. Ask your dealer what blends they carry.

Related: Heating oil vs. natural gas: the conversion decision  ·  11 ways to save money on your heating oil bill