Whether they’re oil or biofuels, our sources of power often come from the ground. In this experiment, you’ll test out more goodies from the ground. Is horse manure a good energy source? If so, how does burning horse manure compare to burning wood from coniferous and deciduous trees?
To find out, we’re going to use calorimetry. Sound complicated? Calorimetry is really just one way of figuring out how much energy is in an object. You may recognize calorie as the word that refers to the unit we use to measure energy in food (the kilocalorie)—but calories can indicate how much energy is present in all kinds of things! We’ll find out how many calories an object has with a calorimeter, which can help us measure heat emitted from an object when its ignited.
Is horse manure a possible energy source?
- Dry horse manure
- Wood from a coniferous (evergreen) tree
- Wood from a deciduous tree (birch, beech, maple, cherry, or alder)
- Kitchen scale that measures in grams
- Safety goggles
- Can opener
- Distilled water
- Graduated cylinder
- Large tin can
- Small tin can
- 1’ of dowel
- Metal wire
- Put your safety goggles on.
- Get your large can and use a can opener to remove the top and the bottom of the can.
- Place the nail on the side of the bottom of the coffee can, and use the hammer to punch some holes around the edge of the base. This will allow air to move into the calorimeter when your samples burn.
- Use the hammer and nails to make a hole in each of two opposite sides of the top of the smaller can. These holes should be large enough to allow the dowel to pass through. Put the dowel through and make sure that the small can rests easily inside the larger one with the dowel suspended on the edges of the larger can. Make sure there's lots of space below the smaller can.
- Weigh three samples of each type of wood and three samples dried manure. Record their weights, and set the samples aside.
- Stick a small piece of thick metal wire into the narrower end of the cork. Stand the cork upright with the wire pointing upwards. Make sure that your wire is thick enough to poke into the pieces of wood.
- Weigh your small can. Add distilled water and weigh it again until the weight is 100 grams higher. You will have added 100 grams of distilled water.
- Measure the water’s starting temperature. Record the temperature in a table like this:
- Put everything on a non-flammable surface in a well-ventilated area. Put on your safety goggles. Place the first piece of manure onto the wire on the end of the cork. Light it on fire. Gently move the calorimeter onto the top of the cork and manure so that the manure is under the small container. Watch from the top to make sure that the flame does not go out.
- After the manure stops burning, take the water’s temperature again and record it in your table. Weigh the burnt manure on the scale and record this in your table as well. Let the calorimeter cool, and replace the water.
- Do the experiment again with another piece of manure. Do the same thing with each of the pieces of wood. Make sure that you use the same amount of water each time.
How can you figure out how much energy each piece of manure or wood gave out? There’s an equation that can help. Remember, for each experiment, you used 100 grams of water.
Heat flow = specific heat x mass x change in the temperature OR
q = (specific heat) x m x Δt
In this experiment, you can use the change in temperature to tell you how much energy a piece of fuel contained. Every type of matter changes temperature in a different way. In this experiment, you used 100 grams of water. The specific heat of water is 4.18 J/(g·°C).
For this experiment, if the water temperature changed from 22 degrees C to 25 degrees C, you’d write the equation like this:
Q = 4.18 J/(g·°C) x 100 g x (25-22 C)
- Enter your real values, and then solve the equation for J (joules). This will give you the amount of energy released by each material you burned.
- Now, compare that energy to the weight of each material. Your 100 gram piece of fuel will likely give out more energy than your 50 gram piece of fuel. For each material, calculate the amount of energy given out for every 10 grams of weight.
- Which material burned the longest? Which one gave off the most heat per unit weight? Is horse manure a good source of fuel?
The horse manure burns longer and hotter than the wood from coniferous trees.
When it comes to using manure as fuel, here’s the scoop: it doesn’t stink, at least not as a fuel. In fact, people around the world use manure as a source of fuel. If you’re burning horse manure, it often lasts longer than fuel from coniferous trees, especially when it’s compacted and made into bricks
The manure needs to be dry, because manure that’s fresh from the horse has a lot of water in it and won’t burn. Manure can take a little longer than wood to catch on fire in any case, so it’s important to use manure that is as dry as possible.
While using manure as a way to warm yourself or your home might sound gross, manure has a lot going for it. It takes a long time to grow a tree, but grass can grow in a matter of days. Get a field and a horse, and you can turn grass into fuel quite quickly—as long as you don’t mind a little bit of mess!
Manure is a good fuel source because it’s essentially grass that’s passed through an animal’s digestive tract. Horses digest grass through fermentation inside their stomach. This process helps break down the cellulose in grass, turning it into a usable (albeit crude) biomass fuel.