The global food system, from fertilizer manufacture to food storage and packaging, is responsible for up to one-third of all human-caused greenhouse-gas emissions. Now, Taylor Farms, a major agricultural player in the U.S. is making an effort to make food without fossil fuels, and shrink its environmental footprint. The company recently completed a makeover of the systems used to power its facilities in California, where it makes fresh-cut salads and other vegetables for major chains as Target and Walmart.