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Biodiesel at Carleton College

Project: Biodiesel Initiative

Project Origins     Where We Are Today     F.A.Q.


Project Origins

biodiesel image

 During a typical calendar year, Carleton College Grounds and Maintenance uses between 2400 and 2800 gallons of diesel fuel --250 to 350 gallons per month during the summer. Although the price of diesel fluctuates, it is currently (as of 1/18/10) at $2.834 per gallon, meaning that Carleton spends 6700-7800 dollars on diesel each year. In addition to this expense, petro diesel is, of course, a source of greenhouse gasses and other pollutants.  As part of Carleton’s ongoing mission to reduce the campus carbon footprint and maintain a sustainable and ecologically friendly environment, Engineers Without Borders – Carleton College began developing a plan to covert waste vegetable oil (WVO) from the dining halls into biodiesel in the winter of 2008.  By converting WVO to biodiesel, Carleton can reduce its emissions while simultaneously saving money.

In addition to the ecological and financial benefits of using biodiesel, the project is also an opportunity for students to apply the knowledge they have gained in the lab and classroom, from independent research in biodiesel chemistry and production to hands-on construction and implementation.  As a result, the continuous production of biodiesel on campus serves both the college and the student body, consistent with the Carleton’s mission of “academic excellence, distinguished by the creative interplay of teaching, learning and scholarship.”


Where we are today

Currently, Engineers Without Borders - Carleton College is prepared to construct a biodiesel reactor for the Carleton College campus. We have a completed a Sustainability Revolving Fund application and have thoroughly researched all aspects of construction and production.  In addition, we are in contact with other chapters of Engineers Without Borders across the United States who have completed biodiesel projects.  As a result, we are prepared to build the reactor at any time.  The project falls well within the Sustainability revolving fund's five year payback period with the capital investment returned within 1.5 years.

Then why doesn't Carleton have a biodiesel reactor now?

Although the plans for a biodiesel reactor are in place, we have not as yet found a suitable location. We are currently working with Carleton administration and grounds in order to secure place on campus.  A biodiesel reactor must be in a well ventilated and firesafe room with enough space for a 5'x5' pallet and sufficient surround workspace. Once we have found an appropriate place to put the reactor we will complete construction, begin producing biodiesel, and put Carleton College one more step closer to sustainable living.



What is biodiesel?

Biodiesel is a clean-burning alternative fuel produced from renewable resources such as vegetable oil.  It is not the same as vegetable oil, and it can be used in place of or combined with petrodiesel and used in vehicles with diesel engines.  It is simple to use, biodegradable, nontoxic, and essentially free of sulfur and aromatics.

How is biodiesel made?

Biodiesel is made from vegetable and animal oils and fats, or triglycerides.  Chemically, triglycerides consist of three long-chain fatty acid molecules joined by a glycerin molecule. The biodiesel process uses a catalyst to break off the glycerin molecule and combine each of the three fatty-acid chains with a molecule of methanol, creating mono-alkyl esters, or Fatty Acid Methyl Esters (FAME) -- biodiesel. The glycerin sinks to the bottom and is removed.

biodiesel chemically 

The Process:

1.    Acquire vegetable oil.

2.    Mix lye and methanol until the lye dissolves into the methanol.

3.    Heat the oil, and mix with the lye-methanol substance.

4.    Once it is mixed, allow it to settle.  Glycerin will form a layer at the bottom.

5.    Test the biodiesel to ensure the reaction is complete

6.    Wash the biodiesel to remove impurities

7.    Dry the biodiesel (remove the water)

8.    Fill up a vehicle with the newly produce fuel!

Why should Carleton use biodiesel?

Carleton’s Grounds and Maintenance departments use between 2400 and 2800 gallons of diesel fuel each year -  250-350 gallons per month in each of the warm months. Although the price of diesel fluctuates, it is currently (as of 1/18/10) at $2.813 per gallon, meaning that Carleton spends $6700-$7800 on diesel fuel each year. In addition to this expense, petrodiesel is, of course, a source of greenhouse gasses and other pollutants. By constructing a bio-diesel reactor, Carleton can reduce its emissions and save money.  The biodiesel will be made by converting the waste vegetable oil (WVO) already produced in the dining halls to fuel.  Biodiesel can be mixed with petrodiesel or used without additives in ordinary diesel engines. In addition to replacing more expensive fossil fuels, biodiesel is a cleaner-burning fuel than ordinary diesel, which is a further benefit to the environment.  The Carleton dining halls produce large amounts of waste vegetable oil, which could be easily recycled and used to create biodiesel.  Creating a biodiesel processor is a relatively simple, environmentally and economically friendly move that would produce large benefits and few downsides.

Does Carleton produce enough vegetable oil to make biodiesel?

Yes!  The Carleton Dining Halls produce approximately 50-70 gallons of waste vegetable oil per week.  This would be sufficient cover a large portion of Carleton's diesel usage.

How does Engineers Without Borders plan on producing biodiesel?

Engineers Without Borders  will create a biodiesel processor, which can be maintained with a relatively low overhead and level of supervision.  Discussions are ongoing with faculty and other campus groups to maintain the biodiesel reactor once built, including the possibility of academic credit or a paid student job.  

Where will the money come from to make a biodiesel processor?

Engineers Without Borders has written a proposal for the Sustainability Revolving fund to support the initial creation of a biodiesel processor.  The but the cost of maintaining the process is relatively low, and will be more than compensated by the College's savings.

Will the project pay itself back?

Yes!  The Sustainability Revolving Fund requires all projects to pay themselves back within five years, and the current project is anticipated to pay back within a year and half, far below the requirement.  Depending on the price of diesel, the project may pay itself back even faster, since the price of diesel is currently rising.  If the price of diesel becomes sufficiently high, the project may be able to support a more ambitious processor design or a student worker position.