Bioheat in Cold Weather

It may only be September, but soon cooler temperatures will arrive and the heating fuel oil season will be in underway. Storing, blending and delivering a high quality product is important. Any breakdown in the system can lead to fuel quality issues, and that can impact your reputation up and down the value chain.

The first step to ensuring high quality Bioheat® fuel oil (biodiesel blended with heating oil) or a non-blended heating oil is tank management. You can purchase the highest quality fuel oil in the market, but if you store the fuel in a dirty tank or neglect tank management, the potential for fuel contamination will increase.

“It is always good to monitor tank quality, whether there is biodiesel blended with the heating oil or not. Your tank is what you are storing your fuel in, and a contaminated storage tank or sediment in the tanks will result in fuel quality issues downstream,” said Kelsey Erickson, team lead, quality support at Renewable Energy Group, Inc.

Tank management tips

Water seepage into the tank can be a significant issue, as this leads to impurities in the fuel. When water permeates the tank and mixes with the heating oil, it can lead to rust formation, fungal growth and accelerated fuel degradation.


“Make sure the tank bottom is dry and free of water. This can be done by simply pulling a fuel sample from the bottom of the tank. Also inspect the inside of the storage tanks for rust deposits, as rust can plug filters up and down the line,” Erickson said.

To solve any potential contamination problems, thoroughly remove any sediment or water from the bottom of the tank. Next, treat the tank with biocide. After the biocide has been used, incorporate a new filter on the tank outlet and replace as needed until the filter is clear of contaminants. If water was present in the tank, it is also recommended that the tank be dried and vented to ensure the water deposits are removed to alleviate the potential for future contamination issues. Another solution can be to use the tanks year-round, with a thorough cleaning performed in between the transition of one fuel type to another.

“We recommend keeping storage tanks completely full, even in the summertime. A full storage tank does not allow extra air to get into the head space, which then reduces the amount of moisture that can condense and settle into the bottom of the tank,” Erickson said.

Attention should also be given to the fuel transfer lines used when loading or unloading blended fuel oil to/from a tanker truck. The transfer lines should be inspected for structural integrity, cleaned and replaced if needed.

Understanding cloud point

The next step to ensuring a high quality Bioheat blended fuel oil product is to understand the cloud point of the fuel and best blending practices.

“The cloud point is the temperature for when the biodiesel fuel will start to become cloudy, but not solid. We recommend that customers store B99 biodiesel 10 degrees above the point,” Erickson said.

To estimate the cloud point of an unadditized blended fuel oil, add the number in Table 1 to the cloud point of your unadditized petroleum diesel. This does not take into consideration the effect of additives. For example: REG-9000™/10 (REG biodiesel) utilized in a B11 Bioheat fuel oil blend will raise the cloud point of the blended heating oil fuel by approximately 16 degrees. This means if the cloud point of No. 2 ULSD is 20 degrees, when mixed with REG-9000/10, the B11 cloud point of the Bioheat fuel oil would be 36 degrees Fahrenheit.

Once you know the cloud point, you can begin testing the effectiveness of cold weather additives. For best results, introduce the additive while the fuel is in motion. Testing the effectiveness of the fuel after pouring in the additive is a simple process. First, take a small sample of the additized fuel and place in a refrigerator for a day; if particles or residue develop, make a new sample with more additive content and repeat the process. If there is no visible benefit at a level of 1 ounce of additive per 3 gallons (or one part additive per 400 parts fuel), then it is best to switch additives.

It’s all about the blend

No matter what percentage of type of additive is blended with the heating oil, to achieve a homogeneous blend, always blend with both fuels at least 10 degrees above their respective cloud points. A blending temperature of 70 degrees or higher is ideal when adding biodiesel to heating oil.

Selecting the correct blending method is an important step to ensuring that the blended fuel will maintain its quality in adverse weather. In-line blending is ideal for creating a consistent blended product, and in many cases is the preferred method when blending cold B99 biodiesel with heating fuel oil.

However, in-tank blending is also a viable option. While more effective when blending warm biodiesel with heating oil, the in-tank method relies on significant agitation and proper loading, and can be done with either the top-loading or bottom-loading blending methods.

“We highly recommend that tanks are kept as warm as possible, as it helps with the flowability of the product. It helps to make sure that the Bioheat fuel oil will not gel in the winter. We still want to ensure that when we are delivering fuel oil to a customers’ home it is able to flow and to be maintained,” Erickson said.

In addition, Bioheat blended fuel oil retailers may want to consider insulating or heating the transfer lines (to and from the tanks and to and from the delivery trucks) to ensure there are no impediments that could affect the flow of the fuel.

Tank maintenance combined with proper heating oil blending can have a significant influence on the performance of biodiesel blends in cold weather conditions. From knowing the cloud point to adhering to the proper care of tanks and lines, heating oil retailers can prolong the functional life of Bioheat fuel oil with a few dedicated protocols.


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