- Teacher Guide
- Student activity, Graph Type A, Level 3
- Student activity, Graph Type B, Level 3
- Student activity, Graph Type C, Level 3
- Grading Rubric
Most of us use fossil fuels every day. Fossil fuels power our cars, heat and cool our homes, and are used to produce most of the things we buy. These energy sources are called “fossil” fuels because they are made from plants and animals that grew hundreds of millions of years ago. After these species died, their tissues were slowly converted into coal, oil, and natural gas. An important fact about fossil fuels is that they are limited and nonrenewable. It takes a long time for dead plants and animals to be converted into fossil fuels. Once we run out of the supply we have on Earth today, we are out! We need to think of new ways to power our world now that we use more energy than ever.
Biofuels are a potential replacement for fossil fuels. Biofuels, like some fossil fuels, are made from the tissues of plants. The big difference is they are made from plants that are alive and growing today. Biofuels are renewable, meaning we can produce them as quickly as we use them up. At the Great Lakes Bioenergy Research Center sites in Wisconsin and Michigan, scientists and engineers are attempting to figure out which plants make the best biofuels. Plants that grow bigger and faster make more tissue, which is called biomass. The more biomass produced, the more biofuels.
Gregg is a scientist who wants to find out how much plant tissue, called biomass, can be harvested from different crops like corn, grasses, weeds, and trees. Gregg is interested in maximizing how much biomass we can produce while also not harming the environment. Each plant species comes with a tradeoff – some may be good at growing big, but need lots of inputs like fertilizer and pesticide. Corn is an annual, meaning it only lives for one year. Corn is one of the best crops for producing a lot of biomass. However, farmers must add a lot of chemical fertilizers and pesticides to their fields to plant corn every year. These chemicals harm the environment and cost farmers money. Other plants harvested for biofuels, like switchgrass, prairie species, poplar trees, and Miscanthus grass are perennials. Perennials grow back year after year without replanting. Perennials require much less chemical fertilizers and pesticides to grow. If perennials can produce high levels of biomass with low levels of soil nutrients, perhaps a perennial crop could replace corn as the best biofuel crop.
To test this hypothesis, scientists worked together to design a very large experiment. Gregg and his team grew multiple plots of six different biofuel crops on experimental farms in Wisconsin and Michigan. The soils at the Wisconsin site are more fertile and have more nutrients than the soils at the Michigan site. At each farm, they grew plots of corn to be compared to the growth of plants in five types of perennial plots. The types of perennial plots they planted were: switchgrass, Miscanthus grass, poplar saplings (trees), a mix of prairie species, and weedy fields. Every fall the scientists harvested, dried, and then weighed the biomass from each plot. They continued taking measurements for five years and then calculated the average biomass production in a year for each plot type at each site.
Featured scientist: Dr. Gregg Sanford from University of Wisconsin-Madison
This Data Nugget was adapted from a data analysis activity developed by the Great Lakes Bioenergy Research Center (GLBRC). For a more detailed version of this lesson plan, including a supplemental reading, biomass harvest video and extension activities, click here.
This lesson can be paired with The Science of Farming research story to learn a bit more about the process of designing large-scale agricultural experiments that need to account for lots of variables.
For a classroom reading, click here to download an article written for the public on these research findings. Click here for the scientific publication. For more bioenergy lesson plans by the GLBRC, check out their education page.
For more photos of the GLBRC site in Michigan, click here.