Q: How feasible is it to compost unmarketable fruits and vegetables on a large scale?
A: Some composting occurs in South Florida on both organic and conventional farms. The major obstacle is economics. Even with quality feedstocks and delivery of horticultural waste and manures to the farm gate for free, it costs well over $40 per ton to compost and distribute it on the farm. The value of the material, whether calculated on the basis of nutrient content (the typical comparison on conventional farms) or soil building value as opposed to green manures, usually proves to be less than cost effective and not economically viable. This may change as the cost of nutrients continues to increase. In addition, most businesses generating waste are unwilling to bring their waste to the farms. They expect the grower to incur the cost; yet conversely, they will pay a tipping fee for disposal of the waste. Composting and compost use would get a boost if waste producers were willing to pay growers a similar fee to accept the waste. As noted above, they still incur substantial costs to make it into compost and spread it on the land. The volume of compost required for each farm should also be considered. The average commercial south Florida organic farm is over 250 acres, while conventional operations range from 500 to 5000 acres. At low rates of compost use, a grower would need 5000 lbs per acre. Some growers use up to 30,000 lbs to the acre. Vegetables are largely water, so they are not comparable in weight to other compost materials. Although the idea of composting vegetables sounds good, the economics may not make it feasible for commercial production systems.
- Gene McAvoy, County Extension Director, Hendry County, University of Florida, IFAS
Commercial composting operations really want manure of some sort because of the relatively high nutrient value. However, they either don't want to pick anything up at all, or if they do, the charge seems prohibitive. Plus, I could not find any that were within what seems a reasonable distance to the south Florida tomato farming operations. It seems that the only way to make this work in the short term would be to try to develop the connections from the ground up rather than rely on existing composting operations. This may not be economically feasible or not.
- Marilyn Swisher, Ph. D., Associate Professor, University of Florida, IFAS