Pomace is the solid residue (seeds, stems, skins) that remain after grapes have been pressed for wine. The good news is that this product stays out of landfills because it has multiple ways to extend its life – such as livestock feed, composting, and distillation. All paths are great, but the question I asked myself is, what is the best way we can take our pomace (with an average of 6000 tons a year), close the loop, and keep it on farm? Enter working red worms – Eisenia fetida.

These wrigglers can use pomace as a food source and break down the organic matter into a nutrient-rich soil amendment. 24 hours a day they tunnel and feed on bacteria and decaying organic matter creating one of the richest amendments you can add to soil. Fresh castings are typically high in bacteria, organic material, nitrogen, calcium, magnesium, and potassium, so it’s important to know exactly the nutrient analysis. For this reason, we created a trial with Michael Dunn at PJ Dunn Working Red Worms to understand if we can create the same nutrient dense vermicompost with pomace, as he does when using cattle manure as the feed.

Starting in September 2023, we delivered 25 tons of fresh pomace to Michael’s redworm farm where he created a section of a windrow that uses 100% pomace as the feed substrate. We are now 9 months into the trial, and the worms are breaking down all matter – seeds, stems, and skins. We have a bit more time before we can pull casting samples to run lab analysis, and when we do, we will compare three types: pomace only, pomace and manure, and manure only.

My hope is that pomace as feed will produce the desirable nutrient analysis to include in our vineyard system. Compost is not currently part of our soil management program, the cost of transportation simply makes it an unreasonable addition for our farm – we have to balance the economics. If these worms can turn our pomace into vermicompost and work to increase organic matter, assist in nutrient cycling, and help liven up our soil, it’s a true win-win.

Check back for details on our nutrient analysis!

See you!

Kendra
Sustainability Manager