Science Buddies: "Ask an Expert"

hello,

i was looking in the forums (i couldn't find anything in 6-8 so i want to 9-12) and saw that someone named 5 cent wanted to do a project on biomass/biofuel. i think that sounds like a really cool project but i'm not in high school, (so some of that i didn't understand ) and i don't have those things. but i love the idea of alternative energy sources!
so i was going to do which biomass material gives off the most biogas, and i saw how to do it on science buddies project site, but i was wondering if, for a visual for my class and teacher, if there was any way that i could make something run on the biogas, a lamp, flashlight , etc...
please help, thanks!

anna

Hi Anna,

This is a great chemistry project! As long as you have your parents permission and follow the safety suggestions (safety glasses, labeling glassware, etc), I think this would make a good project for you, especially since your so interested in the topic.

I think this is the project you are thinking about:

https://www.sciencebuddies.org/science- ... Newsletter

Here is the website that describes how to make the biodiesel:

http://chemistry.about.com/od/chemistry ... diesel.htm

You will need methanol, sodium hydroxide, and new vegetable oil to make the biodiesel; you will need a blender with a glass pitcher. To test the biodiesel, you will need a diesel engine.

Before you get started, do as much background reading on this topic as possible, so you become an expert on the subject. Then check with your science teacher, and make sure this project meets the requirements for the assignment. This is more of an engineering project, not an experimental project. If you have to do an experiment, you can work on this topic, but you will need to think of a question you can answer by doing an experiment.

Please let us know if you have more questions.

Donna Hardy

Is grass considered a biomass material?

anna

Dear Anna,

Yes, grass is biomass. Good luck!

Michelle

Hi Anna,

Michelle is correct; grass and other plants are considered biomass or renewable sources of energy. Here is some general information on this topic:

http://tonto.eia.doe.gov/kids/energy.cf ... ome-basics

Biomass sources like grass and corn stalks contain cellulose and other complex carbohydrates that can be hydrolyzed with acid or enzymes to break them down to monosaccharides (simple sugars). The sugars are then fermented with yeast to form ethanol. I don't think it is possible to get approval to do a science project that involves producing ethanol, but it would be worthwhile to do more reading on the subject.

What do you want to do for your project?

Donna Hardy

My science experiment is going to be:

Which biomass material releases the most biogas?

I'm planning to use corn, soybeans, grass, and other abundant materials. I just didn't know if grass would work. Then I'm going to compare the amount of sugars, and other things that might contribute to my answer.
Thank you.


anna

Hi Anna,

OK. Biogas is methane gas produced by anaerobic fermentation by microorganisms found in cow’s rumen. Here is the project I think you are working on now:

https://www.sciencebuddies.org/blog/200 ... biogas.php

This is an excellent project, but will be very aromatic. You will be comparing different sources of organic material so your project will meet the requirements if an experiment is required.

Do you have a place to do this experiment that is warm enough to allow the microorganisms in the cow manure to continue growing? The write-up on this project idea is very detailed, so please go through the procedure and make sure you can assemble all of the materials. Can you identify your independent and dependent variables? What parameters of the experiment will be controlled?

In this experiment, you will measure the production of methane gas. Do you understand the chemistry of how molecules in the plant material will be converted to methane gas? Please check out the references included in the project write up and let me know if you have any questions.

Donna Hardy

for the experiment do i have to use cow manure? won't the plants decomposing ba able to release gas that will fill the baloon?

thank you,
anna

and also, can i use a fruit in the experiment. the only thing that im worried about is that the water in the fruit will evaporate filling my baloon with water not actual methane gas. should i stick to vegtables? should i not count grass then?

anna

Hi Anna,

You have a very good question and I’m glad that you are asking questions before you set up your experiment. Biogas is methane gas that is produced by anaerobic bacteria found in ruminant animals such as cows. The science buddies experiment specifies using fresh cow manure, as this is a good source of methanogenic (methane-producing) bacteria. The manure also contains microorganisms that will break down the cellulose in the vegetables and grass to the individual sugars so they will be available for fermentation. Here is some more information on this topic:

http://en.wikipedia.org/wiki/Methanogen

If you use just fruit or grass, you will not necessarily have the microorganisms you need to produce biogas. Your samples will be fermented by the normal flora present on the surface of the plant material, and your samples will produce carbon dioxide, lactic acid, hydrogen gas, or a variety of other compounds, but probably not methane. You need the anaerobes in the cow manure if you want to make biogas. Here’s more information on fermentation (breakdown of sugars to produce energy).

http://en.wikipedia.org/wiki/Fermentati ... chemistry)

Please take the time to reread the project guide and check out all of the background references. All of the details are important. It will be helpful if you understand the chemistry of the conversion of cellulose to methane. Remember that you want to ask a question that you can answer with a controlled experiment. Comparing the production of biogas from vegetables and grass would be a good project, but you have to set up your samples with manure to ensure that conditions are optimum for biogas production.

http://en.wikipedia.org/wiki/Fermentati ... chemistry)

Here’s a question for you. If your sample filled the balloon with gas, how would you tell if you had biogas (methane) or carbon dioxide gas?

You will need to explain the science of your project (conversion of cellulose to methane) for your science board, so please do ask more questions if you need additional explanation.



Donna Hardy

what other materials contain the bacteria that would work instead of cow manure? (informational purposes)

anna

Hi Anna,

You can find methane-producing bacteria in the droppings of any animal that can digest cellulose, for example sheep, goats, rabbits, guinea pigs, koala bears, camels, zebras and termites. A local pet store, farm, or zoo could probably help you find a fresh sample. Maybe you could find some termites in pieces of rotten wood. Methanogens are also found in naturally anaerobic habitats such as swamps, the bottom of lakes, and at the bottom of oceans. You would want to use an identical source and quantity of natural methanogens in each of your samples. Are any of these samples readily available to you?

Anaerobic fermentation samples usually smell similar to cow manure, so you will need to do this project outside, but in a warm enough location to allow microbial growth. Remember that the normal temperature for most of the methanogens found in mammals is about 37 degrees Centigrade. The microbes would grow slower at lower temperatures.

The science of microbial ecology is extremely fascinating; however, if you don’t want to work with this type of sample, you should change your project. What do you want to do? Are you going to continue?
Donna Hardy

Hi Anna,

I never answered your question on fruit. You could use any plant material for this project. However, fruit has other uses, so it might be better to choose something that would not normally be used for food, such as glass clippings, vegetable peelings, or corn stalks.

Donna Hardy

thank you sooo much for your help, and i do think that the manure of almost any animal is pretty available to me, i can check my local zoo. Thank you for the ideas of things to use and do!
you are really helpful !!!! Thank you so much!

Thanks for everything,
anna

what if, in the winter i can't get the air up to 37 degrees centigrade (99 F) could i still do the experiment or would the bacteria not grow at all?

anna

Hi Anna,

The bacteria will grow at a lower temperature, but will grow much slower. At 37 degrees Centigrade the bacteria will be able to double in number about every 30-60 minutes if growth conditions are ideal. If the temperature is lower, for example 27 degrees, the bacteria will grow at half the rate, and at 17 degrees, they would grow at 1/4 the rate compared to 37 degrees Centigrade. For your experiment, you will want the bacteria to be growing and producing methane gas faster than the gas can diffuse through the balloon, so a higher temperature will work better.

What is the average outside temperature during December where you live? If it is less than 20 degrees Centigrade (68 degrees Fahrenheit), I recommend that you do something to increase the temperature. You could place the sample bottles close to a water heater in the garage, or place them in an enclosed box with an incandescent light turned on. You need to be careful to not overheat the samples, because the bacteria will die if the temperature is greater than 41-42 degrees Centigrade.

You should get a thermometer and measure the temperature in the area of your experiment once or twice a day. Temperature will be one of your controlled parameters, i.e. the temperature of all samples will be the same. However, since temperature is a critical factor in bacterial growth, you should document it during your experiment.


Donna Hardy

the temperature where i live is normally is anywhere from -7 degrees Centigrade to 2 degrees Centigrade. But i was planning on putting the bottles in a box full of insulation, will that work? the bottles will be kept at a little less than 20 degrees Centigrade. will i need to increase the temperature? will a lamp work o.k.?


anna

Hi Anna,

Try putting a small lamp inside the insulated box and measure the temperature because it would be good to have a slightly higher temperature. Make sure the lamp is not close to anything flammable. However, if it is close the 20 degrees C inside the box and it's not feasible to add a light, I think your experiment will still work.

Do you have time to do the experiment twice? Once to set it up to make sure everything will work as expected, and a second time with all of the independent variables (difference sources of energy) included.

Is there room in the insulated box for the balloons to expand as methane gas is produced?

Donna Hardy

yes to both questions and depending on how much manure and biomass i pit in, will i get a lot more out (i was going to do 115 grams of each)? is it better to use grams instead of cups?

anna

Hi Anna,

Yes, it’s better to use grams as your unit of measure. In science fair projects, you always want to use metric measurements.

I have a question. How are you going to measure your results? You will have a balloon on top of each bottle that will presumably fill up with methane. You can calculate the volume of the balloon to calculate the volume of gas produced.

http://www.equationsheet.com/eqninfo/Equation-0074.html

Try to get balloons that will be perfectly round, instead of oval. You would need to measure the circumference of the balloon and calculate the radius to use the volume equation.

You can then use the ideal gas law to calculate the quantity of methane produced:

http://en.wikipedia.org/wiki/Ideal_gas_law

I don’t know how much chemistry you have had, so let me know if you need help with this calculation.

Donna Hardy

Hi Anna,

I just looked at the experimental protocol, and it suggests using 5 grams of manure and 5 grams of biomass per bottle, so your idea of using 115 grams might be too much. However, since your experiment will be cooler than normal, you might need more than 5 grams. Since you have time to do the experiment twice, why don't you optimize the protocol for the first experiment? Use a range of quantities of manure and one type of biomass (5, 10, 25, 50 grams of each) to determine a good quantity to use that will fill a balloon in 24 hours. Then you can compare results with different types of biomass in the second experiment.

Also, don't forget to controls. What are you going to use for a control in this experiment?

Donna Hardy

i haven't really thought about controls yet, i'm turning in a list of material and procedures tuesday and i just couldn't decide the gram measurement because 5 grams (in most products) only gives me about a tablespoon, give or take a little, which just doesn't seem like a lot. thanks for the offer to help me measure the volume of the gas using a law i've never heard of before. I will have to take you up on that offer, but it might be a little bit because i have to actually do the experiment, so please continue to check this post. thank you!

anna

Hi Anna,

You are correct to concentrate on getting the experiment done and worry about the calculations later. If you measure the circumference of each balloon then you will have all of the data you need to make a graph of your results (moles of methane vs. grams of biomass per unit of time.) If you use oval balloons instead of round ones, you will need to measure the circumference in two directions, and your calculations of balloon volume will be more interesting:

http://en.wikipedia.org/wiki/Ellipsoid

However, you do need a couple of controls for your first experiment. The first control should be an empty soda bottle with a balloon. Since this is a sealed environment, this sample will reflect change in volume of the air due to any differences in temperature or barometric pressure between the beginning and the end of the experiment.

You should also include a second, manure only, control. This sample will show how much methane gas is produced due to the manure alone.

By the way, you should record the temperature in degrees Centigrade and the barometric pressure during your experiment, or at least at the very beginning, and at the end, since these parameters will affect your results.

Donna Hardy

do tigers, lions, jaugurs, bears, or leopards carry the bacteria in their digestive system?

anna

Hi Anna,

The felines are all carnivores and have very short digestive systems. Since felines do not eat cellulose (grass or hay), their digestive systems would probably not contain methanogenic bacteria. Bears are omnivores and do eat plant materials so probably do host a few methanogenic bacteria. However, the manure that you should use for this project should come from a ruminants, such as cattle, goats, sheep, giraffes, bison, yaks, water buffalo, deer, camels, alpacas, llamas, wildebeest, antelope, pronghorn, or nilgai.

http://en.wikipedia.org/wiki/Ruminant

These animals have special digestive systems that are host to bacteria, protozoa and fungi that ferment the cellulose and break it down to molecules that can be absorbed by the animal. Ruminant manure would have a very high concentration of methanogenic bacteria, and you should use a sample that is as fresh as possible.

Donna Hardy

hi,
sorry i keep asking so many questions, but i just found out that my uncle's friend has a pig farm, with lots of pigs. i'm guessing pigs don't work, beacause of what they eat, but i thought i'd ask anyway. So, do pigs have the bacteria in their digestive track?

anna

Hi Anna,

You can never ask too many questions, and this is good one. Pigs cannot survive on pure cellulose, and are usually fed grains and more easily digestible foods. I would expect a very low concentration of methanogenic bacteria in pigs. Is there a goat or a sheep on the pig farm? And, although not ruminants, do you have access to any horses or rabbits? These animals survive on high cellulose diets, so should harbor high concentrations of methanogenic bacteria.

However, here are two websites that describes the production of biogas from pig manure:

http://www.biogas-energy.com/site/pig.html
http://www.thepigsite.com/articles/365/ ... pig-manure

These are not scientific references and the information presented is not very detailed. So it is not clear if the pig manure contains enough methanogenic bacteria on its own to sustain methane gas production, or if the methanogenic bacteria are added pig manure in the anaerobic fermenters. What does your uncle feed his pigs? If the pigs' diet contains a significant percentage of foods containing cellulose, then the manure would probably contain some methanogenic bacteria.

Since it would be easy for you to obtain the pig manure samples, I recommend that you do a trial and see if it will work. With lower numbers of methanogenic bacteria expected, it might just take a little longer to complete the experiment. I would be very interested in knowing if this will work for you.

Donna Hardy

Hi Anna,

How are you doing with your experiment? Do you have a balloon filled with gas yet? Did you decide to try using the pig manure?

I have a question. Do you have any idea on how to identify the gas produced in the balloon? There are bacteria that have the ability to produce hydrogen, oxygen, nitrogen, carbon dioxide, and methane gas. These are all colorless and odorless gases. You are selecting a sample that should contain methane-producing bacteria and you are adding nutrients (grass, etc.) that should be readily converted to methane, so any gas produced will presumably be methane. But, can you think of a way to verify the identity of the gas?

Your project will be better if you can prove the identity of the gas in the balloons. Let me know if you need help.

Donna Hardy

Dear Anna,

The optimum growth temperature depends on the type of bateria. Some prefer temperatures as low as 15 degrees Celsius and others thrive at temperatures as high as 50 degrees Celsius. The generic type is usually best around 37 degress Celsius, as you mentioned. Do you have access to an incubator? Bacterial growth experiments are generally done using incubators. If not, try finding a hot place in your house, for example near a heater, furnace or hot lamp that you can leave on. This is not ideal because the temperature will not be completely constant, but you could try finding a place that is around 37 degrees Celsius and working with that.

Hope this helps!
Michelle

umm... how am i supposed to measure the type of gas? but wouldn't that not matter because biogas is a mixture of mostly methane and CO2, but also can contain oxygen, hydrogen, and other gases? (@ least that is what it said online)
i cant use the pig manure because their diets consist of none cellulose/plant materials, so i found a farmer that will give me fresh cattle manure and that is coming in friday

thanks,
anna