The run off from agriculture and tanners is several orders of magnitude greater.
If you factor the over all benefit to the pollution and resource consumption, a fab is several orders of magnitude better, why else would everyone else scramble to get one built.
A fab at the expense of food security is not a good deal. When you can't feed your people, you are at the mercy of other nations, and that greatly harms national security. India used to once have frequent famines, and had to beg food from other countries. Today it can feed its billion+ population because it is the world leader in producing fruits, vegetables, grains, diary produce etc. A starving population doesn't care about CPU chips.
If you factor the over all benefit to the pollution and resource consumption, a fab is several orders of magnitude better, why else would everyone else scramble to get one built.