I always how how the vegans have so many misconceptions of animal agriculture. Some things that are missing from the equation here is how much resources are actually going to each natural fiber here. With cotton, it is obviously farmed in an intensive, industrial manner (as would hemp be farmed). In an industrial farming operation, there are center pivot irrigation systems, large farm machinery using fuel, taking up land that could be used to grow food crops. So look carefully at the true resource inputs of cotton. With wool, generally those sheep are grazed on a range land setting where the land is too rough, arid, or otherwise is not useful for farmed crops. Wool sheep are not fed a grain diet as it is way too expensive - they are run out on range and do the forage harvesting themselves yielding both wool and protein (meat, which is delicious). In the true open range set up, the inputs are not intense where you have a herder and few fossil fuel inputs and very little use of land that could grow food crops. Then the sheep are shorn by hand, so the harvesting uses mostly human labor even in our modern society (there is no substitute for a good sheep shearer). As for methane production, vegans eat a lot of beans a create a lot of gas - maybe they should quit existing.