Environmental Management and Sustainable Development · Energy and Environment · 2 marks · Numerical answer
Land yields 7000 L bioethanol/hectare with energy content 21 MJ/L, replacing fossil petrol. Bioethanol and petrol footprints are respectively 10 and 80 g $CO_2$/MJ. Find avoided emissions as $n\times10^6$ g $CO_2$/hectare, reporting n to one decimal place.
Bioethanol energy yield is $7000(21)=147000$ MJ/hectare. Equal-energy substitution avoids the difference in footprints,$80-10=70$ g CO₂/MJ. Thus avoided emissions are $147000(70)=10290000$ g CO₂/hectare,$10.29\times10^6$. Rounded as requested,**n=10.3**. Subtracting the bioethanol footprint prevents counting gross petrol emissions as net savings.
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