Recycling Fish Waste to Fertilize Guam Farms

SUMMARY

Through this project, we intended to test the viability of recycling fish waste developed into a fish emulsion fertilizer on sweet corn, eggplant and other crops. We hoped to make a low cost fertilizer from this waste product to keep it from going into the landfill. Ultimately, we determined this is not an effective use of the fish waste. The product is difficult to handle and labor intensive. A potential better use is in livestock feed as a protein additive by drying and grinding the fish waste.

I purchased a 500-gallon vat for $1,000 and then obtained a large quantity of the fish waste for $500. I purchased 50 gallons of sulfuric acid for $400 and mixed it with the fish waste. Once it dissolved the fish, I diluted it and used it in my fertigation system. At first it seemed successful, but it ultimately destroyed my injector, costing $130, and clogging 21 rolls of drip line, costing around $8,400 total. The oils and semi-solid gels and acidic material left over from the processing caused this.

I tried applying the diluted waste slurry directly to the soil. This is more labor and machinery intensive as it required a driver, one worker stirring the mix and one worker applying the slurry. While I see some results in the plants, I do not think the effort is justified. My material cost was $10,430. My labor included gathering materials and supplies and treating the fish waste with acid, necessitating 30 work hours. I also spent 96 hours diluting and applying the mixture; installing the drip and fertigating effort took 156 hours.

Ultimately, there are probably better uses for the fish waste, perhaps as a soil amendment through composting, or as a blend in livestock feed supplement. We also noticed that the fish waste drew fire ants.

RESULTS

I found that treating tuna industry fish waste with a sulfuric acid bath and then diluting it does not make an emulsion suitable for use with fertigation injectors and drip irrigation lines. The product has too much oil and small particles that, I believe, ruined my irrigation lines. When I tried to apply the product directly to my rows of sweet corn, I did not get significant improvement in crop growth or yield. Given the time this effort involved, it is not a feasible source of fertilizer for the islands.