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Math Help - Co2 Calc check

  1. #1
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    Co2 Calc check

    Hi Guys, I am doing research on Carbon footprints etc for my company and would like someone to check my working on the following as the answer seems high.

    Question:
    What is the carbon footprint of a cardboard Tray used to display cosmetics?
    Base this on production of 500 Trays.

    Known Values:

    1 Metric Ton of std display cardboard = 4100kWh to produce
    1kWh (coal fired power station) = 970g Carbon Dioxide
    1 Metric Ton of std Display Cardboard = 690 sheets
    1 Cardboard tray = 2 sheets of cardboard

    My working is as follows:

    1 ton of cardboard = 4100kWh
    4100kWh x 970g CO2 = 3,977Kg CO2
    500 Trays = 1000 sheets = 1.45Ton of card
    3,977Kg CO2 x 1.45T of card = 5,766.65Kg = 5.77Ton CO2
    5.77Ton CO2/500 Trays = 11.53Kg CO2 per tray.

    Just to put things into perspective the equivelant trays formed in High Impact Polystyrene produces 200g of CO2 per tray.
    The above being based on findings from a study done by the Michigan state university.

    What I don't understand is why cardboard appears to be more damaging to the environment than plastics yet conventional wisdom shows the opposite to be true.

    Greatful for any help on this.

    Best Regards

    Martyn
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  2. #2
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    Quote Originally Posted by Marvlin View Post
    Hi Guys, I am doing research on Carbon footprints etc for my company and would like someone to check my working on the following as the answer seems high.

    Question:
    What is the carbon footprint of a cardboard Tray used to display cosmetics?
    Base this on production of 500 Trays.

    Known Values:

    1 Metric Ton of std display cardboard = 4100kWh to produce
    1kWh (coal fired power station) = 970g Carbon Dioxide
    1 Metric Ton of std Display Cardboard = 690 sheets
    1 Cardboard tray = 2 sheets of cardboard

    My working is as follows:

    1 ton of cardboard = 4100kWh
    4100kWh x 970g CO2 = 3,977Kg CO2
    500 Trays = 1000 sheets = 1.45Ton of card
    3,977Kg CO2 x 1.45T of card = 5,766.65Kg = 5.77Ton CO2
    5.77Ton CO2/500 Trays = 11.53Kg CO2 per tray.

    Just to put things into perspective the equivelant trays formed in High Impact Polystyrene produces 200g of CO2 per tray.
    The above being based on findings from a study done by the Michigan state university.

    What I don't understand is why cardboard appears to be more damaging to the environment than plastics yet conventional wisdom shows the opposite to be true.

    Greatful for any help on this.

    Best Regards

    Martyn
    your math definitely looks correct. However, you are correct that that number does seem extremely high. I would say that maybe since the fact that plastics are a bi-product of the production of gas, they do not count a lot of the emissions, as its main use is to produce gas. Also, maybe it is due to the fact that polystyrene is a very light substance so there is little of it used compared to the cardboard.


    Also, I think the biggest flaw that I see is maybe in the statistics themselves. I am not sure what area you are from, however, I know that the majority of energy is not created at coal emissions plants where I am from. I think maybe 2% of our electricity comes from coal, and the rest produce very little, if any CO2. So maybe the people calculating for the polystyrene assumed this. I do know that people will try a lot of tricky things like that in order to make their numbers seems lower. However, I do not know who did the calculations for the polystyrene. I also, think that maybe your numbers are off, as I would assume some of them would be much lower. However, I hope my thoughts will spark something that will help. (Can you maybe get more of these boxes out of a sheet of cardboard, because that seems like a lot of wasted cardboard to me).
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  3. #3
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    Hi, thanks for taking the trouble to check my figures.

    I hear what you are saying and I am in total agreement as regards the accuracy of the original figures.

    The cardboard consumption per kit I agree seems a little high but this is down to the need to essentially have multiple layers of card to create a suitable depth to locate the product. If you imagine stacking up layers of card to say a 1 inch depth than cutting a circular hole through it, leaving a location to place for example a tube of hair mousse that is essentially what we are up against.

    As a result the cardboard consumption is phenominal.
    With plastic, although it has a higher Carbon footprint per ton the amount req'd per stand is a lot less.
    Indeed, only 1 sheet half the size of the cardboard sheet is required to make 3 trays.
    Therefore, making the carbon footprint per kit significantly lower than the equivelant in card.

    My problem is, I am to a large extent reliant on figures taken from the internet as I do not have my own laboratory nad wouldn't know what to do with it if I had )

    I have tried to cross reference all the figures used and indeed have found multiple references to back up my findings with very few to dis-agree with them.
    However, I have to consider that mis-information can spread much as it has with me from site to site.

    Once one sit emakes a claim, another will read it, assume it as fact and use it in their project.

    This will go on and on untill there are multiple sites with the same inacurate data seemingly making the data valid.

    Anyway, I am wrapping this project up now and our clients will be in reciept of the document later this week with copies of all the sources of information so they can judge for themselves as to their validity.

    Many Thanks

    Martyn

    As regards CO2 emmissions I got them from this site, which made for interesting reading,i.e. alot of power consumption is not as clean as you might first presume.
    Last edited by Marvlin; May 26th 2008 at 11:40 PM.
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  4. #4
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    Ah I see... I didn't realize you were in the UK. I suppose that the way you make power there would be quite significantly different than we do in North America. I know here we use a lot of methods to create electricity that require little or no carbon dioxide/monoxide. (ie. nuclear power, hydroelectric plants, etc). I know the amount of coal we burn is very small due to the number of other ways we create power. However, I unfortunately know very little about the ways electricity is made in other parts of the world.
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  5. #5
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    OK... I actually did a little more reading on that site, and I would still say that your assumption that all of your electricity comes from coal powered electricity plants is a poor assumption. This is because the gas powered plants emit only 385 grams per kWH and the oil fired only 740g per kWH. It also mentions that there are renewable energies used that reduce the amount of coal that is required to be burnt, and in general renewable energies emit very little to no carbon emissions.

    It also says that "ii) As mentioned earlier 45% of Scotland's electricity is produced from fossil fuels - so figure needs to be adjusted to reflect this." This definitely means that you should not be assuming 100% for your carbon emissions. I have not done enough in depth reading of the article to know how much, however, if you read you should be able to come up with a better estimate... by using 45% of the fossil fuels emissions +55% of the remaining items emissions.
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