Science fair title

[deleted-326820]

Hello,
We are looking for a science fair title for a project using kitchen scraps to make biofuel. Any suggestions would be greatly appreciated. Thank you

[SciB]

Kitchen scraps into fuel--how, by composting them into methane? Or do you propose feeding the scraps to algae or bacteria and harvesting them to make biodiesel?

"Kitchen diesel--converting cooking scraps to biofuel."

"Supper and rocket fuel--waste turned into gas."

"From kitchen to fuel tank--food scraps turned into usable energy."

Good luck!

Sybee

[deleted-326820]

Thank you for your reply. We fermented organic kitchen waste. The idea is to see how much ethanol can be produced from food waste. What do you think of this idea? Thank you!

[deleted-326820]

We also need help in coming up with a question and a hypothesis. Thanks!

[SciB]

Hi,

When you say that you 'fermented' kitchen scraps can you please describe exactly how you did it? Vegie scraps will decompose on their own but I doubt if that decomposition will produce much ethanol. Did you add bread yeast or brewers' yeast to the scraps?

How did you plan to measure ethanol production? Fermentation by yeast yields carbon dioxide gas and that is relatively easy to collect and measure the volume of.

Making fuel such as ethanol from organic matter is a hot area of research now and there's lots of info about it on the web. Here are some of the variables you could consider:

1. type of vegie scraps
2. coarsely chopped vs finely chopped scraps
3. degree of moistness of the scraps
4. temperature--yeast and bacteria work better at temperatures above 75F (24C)
5. what kind of yeast or bacteria you add to do the fermentation

Your hypothesis could involve one or more of these variables--it's up to you to pick what interests you to study.

Post again with details of your procedure so we can better answer your questions.

Sybee

[deleted-326820]

Hello Sybee,

Thank you for your reply.

Over a period of about a month we collected both veggie and fruit kitchen scraps which we blended and then froze. Once we had collected about 7kg of material we added enough water to make a total volume of 9L. We homogenized and pasteurized the mixture by boiling for 5 minutes. Using brewers yeast we fermented the organic material in 3 - 3L Plastic bottles and measured the %sugar and specific gravity daily (And a control). After 4 days, we siphoned off 2L of each and transferred into a secondary fermentation jar with a air lock. We recorded the specific gravity and %sugar over the next 10 days.

Our project question was: How much biofuel in the form of ethanol can be produced through fermentation of plant-based kitchen waste?

As we had not considered having an independent variable prior to our experiment we are hoping this will be an acceptable question.....?

We have done quite a bit of research on biofuels versus fossil fuels, global warming and climate change, disadvantages and advantages of biofuels and their energy sources, household organic waste etc. which is why we wanted to do the experiment.

Thank you for your help. Please let us know if you need any further information. I only included a brief description of our procedure.

Sincerely,

Kester

[SciB]

Hi Kester. Thanks for the details about your project. I wish everyone would explain their methods as well as you did!

The production of ethanol from fermentation of waste plant material is a major area of research today. Corn has been used mostly, but this is wasteful of what is normally a food crop when other plant materials could be used. Your model system showed that simple fruit and vegie waste could be turned into ethanol.

Since as you said you did not set up any independent variables, your project constitutes a demonstration that provides proof-of-concept. If you were a scientist, you would now go on to test all the parameters to maximize ethanol output such as type of feed stock, ratio of yeast to organic matter, species of yeast, addition of enzymes or bacteria to convert cellulose to sugar, optimal temperature, stirring, etc. How to scale up the process to utilize large amounts of organic matter to produce the most ethanol would be one of the big challenges.

I hope you decide to continue with this project. I have been composting fruit and vegie scraps for many years to use on my garden and I would love to see all the wasted organic matter in this country turned into some usable product. With more and more energy coming from wind and solar and now in the form of biofuel, our dependence on petroleum may finally come to an end.

Good luck!

Sybee

[deleted-326820]

Hello Sybee,

Thank you so much for your words of encouragement and your suggestions. We are thankful for your time and your expertise.

We are also looking forward to the day when our dependence on fossil fuels comes to an end. Reading through some of the research papers, left us surprisingly optimistic to learn just how much effort is being focussed on finding sustainable, renewable and green energy sources. We know our experiment is not new, but it is interesting to calculate just how much energy is being lost by the enormous amount of food and organic waste being thrown into landfills every year. Never mind the huge environmental problem this also causes. Whether or not fermentation of household organic waste is an economical solution, is another question . But, perhaps its a better place to look than using valuable land to produce vast monocultures for biofuel when we should be growing food to feed our world. I think we all have to do our part to keep our world a healthy place to live, for future generations, although sometimes its not even clear what the right thing to do is. I worry for my children.

I will keep you updated on our results once we do some calculations for your interest if you like. If you have any further suggestions, they will always be welcome.

Thank you,

Kester

[SciB]

Hi Kester and thank you so much for the kind words! I am glad I could help you. Please don't hesitate to ask any questions at all. If something doesn't sound right, maybe it isn't, so get a second opinion from us!

I share your optimism that our children are very concerned about creating a world where enough food can be grown for everyone using a sustainable composting system rather than over-dependence on chemical fertilizers. I have heard the statistic quoted that in the U.S. 40% of our food is wasted. That is terrible!! First it is wrong that so much has to be wasted and second, at the very least, the 'waste' food should be turned into biofuel or composted and recycled that way. Some landfills have set up methane digesters to use food scraps to generate flammable gas that can power an electric generator.

Maybe you could develop a home fermentation unit that would sit on the counter in the kitchen next to the cutting board. As you make your salad or cut up vegies for a stew, put the scraps into the fermenter and it would automatically homogenize them, mix them with yeast and bacteria and send the slurry to a temperature-controlled fermentation tank. When the fermentation was done, the mixture would go to a holding tank and when it was full you would take it to a processing unit and pick up an empty tank for the next batch. Just a dream at this point, but if we can inspire our kids to work on science projects to test these ideas, maybe they will become reality someday.

Good luck!

Sybee

[deleted-326820]

Hello Sybee,

Thank you for your post. We love your idea of having an automated countertop fermenter for kitchen waste!

We have some questions on how best to interpret and represent our results. We have completed the experiment and are now in the process of putting together our results, conclusions and abstract. If you have few minutes, we would love to hear your thoughts on the following.

The fermentation experiment produced 5% ethanol. We fermented 7.3kg of plant-based kitchen scraps. Once liquefied,the total volume was made up to 8L. This was then divided equally into 3 - 3L fermentation jars (2.6L each). After a few days 2L of the mixture was siphoned off and transferred into 3 - 2L secondary fermentation bottles (with an airlock) leaving the sediment behind.

How do we interpret our results? As we did not distill the ethanol, how do we calculate the amount of ethanol produced? That is,how do we calculate how much ethanol was produced from 9.2kg of kitchen waste? Is it as simple as taking 5% of 6L? 300mL? Ie. 7.3kg of plant based kitchen scraps produced 300mL of ethanol.

We have plotted %sugar vs. %ethanol with constant temp. to show our observations.

Our second question is in regards to how we connect/relate our data to the world around us, specifically how much biofuel could be produced from organic waste. We live in rural western Canada. During our research, we found a number of different statistics relating to food waste, organic waste etc. produced in Canada, US and worldwide. Which values would one use? A more local approach (Canada) or North America or Worldwide? Also many of these values represent all organic waste including other compostable materials such as yard trimmings, agricultural waste etc. We wanted to show how much biofuel could be produced if organic kitchen waste was diverted from landfills but in the scope of our experiment. Ie. Without going into details about other kinds of biofuel production.

My apologies for the lengthy post! I'm sorry if I'm not being very clear; I hope it doesn't sound too confusing! Thank you so much for your time; we look forward to hearing from you.

Sincerely,

Kester

[SciB]

Hi Kester,

Your post was very clear! Thank you for explaining your project so well and including all the details. It makes it so much easier to answer questions when we have all the relevant information right in front of us.

The kitchen scraps you fermented constitute a complex mixture of carbohydrates, sugars, protein and minerals so it is not possible to say how much ethanol was produced without doing a measurement. Where did you get the 5% ethanol figure? I think if you feed bread yeast pure sugar it can produce 5-7% ethanol before the alcohol inhibits its metabolism. But you do not know how much fermentable sugar was in the kitchen scraps, right?

I am afraid the only way you could have calculated ethanol production would have been to measure the amount of carbon dioxide produced and use that in the reaction equation to determine ethanol. You can measure ethanol by distilling it but most people don't have a distillation apparatus.

Do you have a week or so before the project is due? I would suggest repeating the experiment on a smaller scale but using the same type of kitchen scraps as before and proportionally the same amount of yeast and volume of liquid. You will need to do the fermentation in a sealable container like a 1 L plastic bottle. Now you need to set up a way to collect and measure the CO2 formed. There is a Scibuddies project that shows how to do this: https://www.sciencebuddies.org/science- ... #procedure

There's also a Youtube video that shows how to do the gas collection into a graduated cylinder filled with water: https://www.youtube.com/watch?v=UQRCUxrLU1c

In regards to your question about using kitchen waste for fuel production you could do a sort of back-of-the-envelope calculation of how much kitchen waste is produced in a year by the total number of households in Canada and the US. I don't know if anyone has determined such statistics but you could use your own family as a typical producer and ask your friends to estimate how much scraps they produce. My family likes salads, fruits and veg, and we have tea and coffee so I have probably 200 g of scraps every day, which I am proud to say all go into my compost heap and thence onto the veg garden! That works out to 73 kg of potentially fermentable scraps per year. Multiply that by the number of households in Canada and the US which has to be in the millions and you have a LOT of potential fuel production.

Now if I can just engineer an automated kitchen counter fermenter or a way to get everyone's scraps to a central processing station, we'll be able to use this huge amount of wasted material. Even if people composted their scraps it would be a better use than throwing them in the trash.

I hope this helps finish up your project and I look forward to working with you on the next one!

Sybee

[deleted-326820]

Hello Sybee,

Thank you for your reply.

We used a hydrometer to measure the specific gravity of our mixture before, during and after fermentation. Using the difference between the initial specific gravity and the final specific gravity, we calculated the percent alcohol as in beer and wine making. Although probably not the most scientific, will this be sufficient?

We do have time to do another fermentation experiment and measure the amount of CO2 produced. I do have to admit, though, it has been a long time since I have done those types of calculations and I'm not sure my 12 year old would understand....?!

I would like to think that all households produced as little waste as your family! During our research we found that Canada produces approximately 7 million tons of organic food waste with about 7.3 billion kg coming from fruits and vegetables.

We look forward to hearing from you. Thank you.

Kester

[SciB]

Hi Kester,

I'm not sure if the hydrometer measurement will be usable in your kitchen scrap juice because it is a mixture of many things that are denser or lighter than water--not just sugar or alcohol. Do the instructions for the hydrometer say that you can measure alcohol content in a mixture like mash?

Yes, if you decide to do another yeast reaction in order to measure the amount of gas produced, you'll have to get out your old chemistry textbook to refresh your memory on how to work with chemical equations!

C6H12O6 + yeast → 2 C2H5OH + 2 CO2

This tells you that for every 2 moles of CO2 produced you get 2 moles of ethanol. So all you have to do is measure the volume of CO2 produced in liters and divide it by 22.4 which is the volume in L of one mole of any 'ideal' gas at standard temperature and pressure (21 C and 1 atm). In the lab you would correct the volume for non-standard conditions but for this purpose, 22.4 L/mole is good enough.

This calculation will give you the moles of CO2 in the gas you collected from the yeast reaction. According to the equation, equimolar amounts of CO2 and ethanol are formed so the number of moles of CO2 is equal to the number of moles of ethanol produced.

One mole of ethanol is 46 g so all you have to do is multiply this by the number of moles (or fractions thereof) of CO2 to get the weight of ethanol in the juice. You probably want to know the volume rather than the weight, so just divide the weight by 0.789 g/mL (density of ethanol) to get the mL of ethanol.

I'm pretty sure my calculations are right but if you have more questions, be sure to ask. Biologists are not experts in chemistry any more than chemists are experts in biology!

Sybee