November-December 2001

The topics in this newsletter are considered to be timely and of interest. Comments and suggestions are invited. The use of trade names in this newsletter is not an endorsement of any company or product by the Maryland Cooperative Extension, University of Maryland, College Park.
David S. Ross, Extension Agricultural Engineer

This issue:

Biodiesel – Giving Oils and Fats a Good Name
Energy Conservation in Greenhouses

BIODIESEL—Giving Oils and Fats a Good Name

Biodiesel is an alternative to petroleum-based diesel fuel that is already widely used in Europe and is becoming increasingly popular in the U.S.  Interest in alternative energy sources in general is increasing due to global environmental concerns and energy security issues.  However, major roadblocks to the widespread use of many alternative fuels exist, including the need for engine modifications, which have associated costs and often decrease equipment performance.  These roadblocks do not exist with biodiesel, which can be used in the same combustion-ignition engines used for petroleum diesel fuels without modification (although, as discussed below, certain biodiesel blends may not be compatible with fuel hoses and pump seals over the long-term).  The opportunity to move away from our dependence on fossil fuels without sacrificing engine performance explains why interest in this environmentally-friendly fuel is growing.

Where's the "bio" in biodiesel?  Unlike petroleum, the starting materials used for biodiesel production—new or used vegetable oils and animal fats—are non-toxic, biodegradable, and renewable.  Biodiesel is produced by chemically reacting the oils and fats with an alcohol like methanol in a process similar to that used to make soap.  As a result of these reactions, biodiesel is also oxygenated, which means that it burns more cleanly and completely than petroleum fuel, and emissions of pollutants, including gases that cause global warming, are reduced.  Instead of the noxious exhaust odor of petroleum diesel, biodiesel emissions smell like doughnuts or French fries!  Another advantage of biodiesel is that it contains much lower levels of sulfur compared to petroleum diesel.  The sulfur in petroleum diesel is corrosive to engines and when emitted, leads to the formation of acid rain and forms particulates that can cause health problems when they are inhaled and find their way into our lungs.  In addition, producing biodiesel from soybeans or other crops increases agricultural revenue and creates jobs. 

How does biodiesel perform?  In extensive field tests, fuel consumption, horsepower, torque, and haulage rates using biodiesel were similar to those observed with conventional diesel.  Because it has similar properties to petroleum diesel, biodiesel can be used in a pure form (100% biodiesel, known as B100 grade); however, blends of biodiesel and petroleum diesel are much more commonly used, for several reasons.  First, blends of up to 20% biodiesel mixed with petroleum diesel can be used in nearly all diesel equipment without any modifications, whereas high levels of biodiesel can soften the materials in fuel hoses and pump seals over time.  Second, compared to petroleum diesel, biodiesel is more prone to breakdown and formation of gummy residues that can cause clogging problems, due to its higher oxygenate content.  However, this problem is minimized by using low biodiesel blends, which are more stable than B100.  The most commonly-used blend is a mixture of 20% biodiesel and 80% conventional diesel, which is known as B20.  The lubricity of biodiesel is greater than that of petroleum diesel.  Therefore, an added benefit of blending biodiesel with petroleum diesel is improved lubricity.  This will become increasingly important in the future as refiners continue to decrease the amount of sulfur, which acts as an engine lubricant, in on-highway and off-highway grade diesel fuels in response to existing and expected EPA regulations. 

What is the biodiesel market and availability?  In Europe, where approximately 34% of cars have diesel engines, biodiesel is widely available, even for use in passenger cars.  One thousand filling stations sell canola oil-based biodiesel in Germany alone.  In Maryland, biodiesel is currently available at only one commercial pump, which is located in Westminster, Maryland, and is sold as a 5% soy-based biodiesel blend (called B5).  The cost of the biodiesel blend is approximately the same as for the conventional diesel sold at that location.  However, biodiesel can also be purchased in pure or blended form in the Maryland area from Tri-Gas Oil Company.  Fuel can be purchased in volumes ranging from a few gallons to a transport carload; however, prior arrangements must be made in order to make small volume purchases.  Biodiesel can also be purchased by the transport car or tank wagonload for delivery to a farm from Southern States Cooperative.  Members of the agricultural community are increasingly purchasing biodiesel, in part due to a rebate program offered by the Maryland Soybean Board.  This program creates an additional incentive to use biodiesel by reimbursing first-time biodiesel users for 50% of the difference in the cost of soy-based biodiesel (B20 blend) and petroleum diesel.  The minimum rebate that can be obtained through this program is $100, and rebates will not exceed $1000.  In addition to farmers, other major biodiesel users in Maryland and the U.S. include the U.S. Postal Service and the U.S. Departments of Energy and Agriculture, as well as many school districts, transit authorities, national parks, public utility companies, and garbage and recycling companies.  Using biodiesel enables federal, state, and public utility fleets to meet federal requirements for using alternative fuels.

What is the future for biodiesel?  Although the idea of using biodiesel may seem new, it is not.  Dr. Rudolf Diesel demonstrated his engine at the 1900 World Exhibition in Paris using peanut oil fuel.  Petroleum diesel evolved to be the diesel of choice only because it was the cheapest option.  Due to dwindling petroleum reserves and improved air quality standards, biodiesel is likely to become increasingly competitive, and in some cases, may already be the least-cost solution to managing air emissions.  In addition, new developments in biodiesel research promise to improve the usefulness and decrease the cost of biodiesel even further.  For example, the U.S. Department of Agriculture's Agricultural Research Service is developing additives that will help overcome the incompatibility of high biodiesel blends with certain hoses and seals, while the Department of Energy is conducting research involving spicy mustard seed.  Mustard seed oil, which previously was a low-value, inedible waste product, has properties that make it ideally suited for biodiesel production.  The mustard meal that remains after the oil is extracted is a high value, organic pesticide, which will help keep mustard-based biodiesel costs low.

For more information on purchasing or using biodiesel in Maryland, see the contact information below.

Jennifer Becker
Extension Engineer

Biodiesel-related phone numbers and addresses:

Energy Conservation in Greenhouses

In a northern greenhouse operation, energy costs run second only to labor costs in producing plants.  About 70 percent of the energy is used for heating, 10 to 15 percent is electricity used for lighting, operating fans, pumps and other equipment; and 5 to 10 percent may be used by trucks or tractors, depending on whether the operation is retail or wholesale.  Energy is essential for plant production, but conservation practices are important for limiting excess use of energy.

Factors affecting heat loss.  A greenhouse is a large relatively poorly insulated structure so heat loss can be large.  Solar radiation (infrared (IR) radiation and light) enters a greenhouse and is absorbed by plants, soil, and the greenhouse fixtures.  The warm objects then reradiate this energy back toward the sky.  The amount of radiant loss depends on the glazing material, the outside temperature, and the amount of cloud cover.  Glass and rigid plastic materials exhibit the “greenhouse effect” which means that they block most of the long-wave thermal radiation that tries to leave the house through the glazing, allowing less than 4% of thermal radiation to pass through.

In contrast, more than 50% of thermal radiation will pass through a single layer of polyethylene.  Moisture typically condenses on the inside of the glazing and it will reduce the heat loss by 25 to 50%.  Of course the condensation also reduces the light transmission and, thus, the amount of solar radiation entering the house.

Polyethylene film glazing can be improved by adding an IR-absorbent material that blocks up to 20% of heat loss without lowering the light transmission.  The IR-absorbent material adds only about $0.01 per square foot to the cost of the material and will pay back this cost in only a few months.  Many of these films also have an anti-condensation additive to cause the water to drain off rather than drip.

Small greenhouses have more surface area relative to the floor space.  For instance, a range with six individual freestanding houses, each 30 feet by 100 feet with 10-foot-high sidewalls, has a 37% greater surface area than a gutter-connected house providing the same floor area for growing.

Make sidewalls high enough to give adequate headroom.  Adding a foot or two of sidewall height increases heat loss only by approximately 5%.  High sidewalls give better clearance for hanging baskets, thermal blankets, automatic boom watering devices, and other applications.

Heat loss by air infiltration is much less for houses covered by large sheets of film plastic as compared to small glass panes.  The ventilation system also has a large effect on infiltration.  Inlet and fan shutters must close tightly or they will allow a large air exchange.  Poor design, ice, snow, damage, or lack of lubrication can all contribute to the problem.  Window vents seal better than inlet shutters, but even they require maintenance to ensure a tight seal when closed.

Environmental Controls.  The best heating system has little value if its controls do not work properly or are incorrectly located.  Temperatures below optimum levels reduce productivity and delay crop maturity, which results in market losses.  Temperatures above optimum levels waste energy and also cause crop timing and quality problems.  For example, when the outside air temperature is 40^o F, a greenhouse maintained at 62^o F will use 10% more fuel than the same house maintained at 60^o F.

Many thermostats using a bimetallic strip sensing element have wide differentials of 3^o to 6^o F between the ON and the OFF settings.  A thermostat with a 5-degree differential set at 70^o F will turn on at 65^o F and turn off at 75^o F.  This is a wide range of temperatures ranging from cooler to warmer than the crop requires.  A better choice for greenhouses is a sensor activated by pressure from the expansion of a liquid or gas in a coil of closed tube.

Shield the thermostat to protect the sensor from the sun.  Install the thermostat inside an aspirated box that has a fan to draw greenhouse air past the sensor.  Paint the box white and place it near the center of the house but away from direct influence of heaters or ventilation vents.

Further reading and ideas:  This article was adapted from the extensively revised Energy Conservation for Commercial Greenhouses, 84 pages, NRAES-3, available from NRAES, Cooperative Extension, 152 Riley-Robb Hall, Ithaca, NY 14853-5701 for $17.00 per copy plus $3.75 postage and handling for single copies.  Contact NRAES by phone at 607-255-7654, by email at nraes@cornell.edu, or on the web at www.nraes.org.  John Bartok, Jr., extension agricultural engineer with extensive experience in this field, authored this book.