There is one requirement that must be met for a fuel to be considered a biofuel. that is a) the starting material must be co2 that can be fixed or turned into other molecules. b) the biomass is produced year after year through sustainable farming practices. c) it does not harm ecosystems, contribute to acid rain, or worsen global warming. d) they do not produce any greenhouse gases when used.

step 1 ammonium can be absorbed by plants, but some is converted into nitrates which are better for plants to absorb. this is called nitrification. 2. step 2 the deer eats the plants and uses the nitrogen-containing proteins for cell growth. 3. step 3 bacteria in the soil conduct nitrogen fixation to convert nitrogen gas from the atmosphere into ammonium. 4. step 4 some of the nitrates are absorbed back into plants, but denitrification breaks down the nitrates into nitrogen gas released back into the atmosphere. 5. step 5 nitrogen is found in the urine, which gets broken down into ammonium through the process of ammonification. 6. step 6 plants absorb the ammonium and begin assimilation, the process to add the nitrogen to protein.

c. heat from the poles back down towards the equator.