Data for: Greenhouse gas emissions and nutrient retention during food waste fermentation

Description

We undertook a lab scale bokashi fermentation of model food waste made from cabbage and potato to measure greenhouse gas emissions and track the fate of carbon and nitrogen in the food waste. The carbon and nitrogen contents within the gaseous, leachate, and solid (fermentate) fractions were measured. The aims of this study were to (i) quantify greenhouse gas fluxes per kg of food waste from a model food waste during anaerobic fermentation, and (ii) determine the proportional carbon and nitrogen contents of the solid (fermentate), liquid (leachate) and gaseous (greenhouse gas emissions) fractions.

Steps to reproduce

Model food waste was made by combining 5 cm3 size cubes of 150 g red cabbage, 150 g raw Maris Piper potato, and 150 g cooked Maris Piper potato. Bokashi bran, inoculated with the EM-1® mixture of Effective Microorganisms, was obtained from EM Agriton Ltd. Fermenters were made from one litre cylindrical polypropylene sealable tubs, with Suba Seal® septa in the lids and a clampable plastic drainage tube in the base. A steel mesh platform was used to raise food waste above the base of the tub by approximately 3 cm. A nylon mesh cloth was used to line the fermenters and contain the food waste. The food waste mix (450 g per fermenter) was layered with Bokashi bran and compressed into fermenters. Five different bran/food ratios were used by altering the quantity of bran mixed with 450 g of food waste per fermentation vessel. Bran additions of 0 g, 4.5 g, 9 g, 12.86 g or 45 g of bran, equating to a control and ratios of 1:100, 1:50, 1:35 and 1:10, respectively were prepared in triplicate. Fermentation vessels were incubated at 18°C for 21 days with vessels remaining closed throughout this period. Fermenters were drained at 2, 5, 8, 11, 14, 18, and 21 days to sample accumulated leachate. Leachate volume was measured and stored at 4 °C in sealed polypropylene tubes prior to pH analysis using a HANNA HI-2550-02 Benchtop pH Meter. Leachate samples were then stored at –20 °C prior to further chemical analysis. Aliquots of leachate samples were analysed for total organic carbon using a Shimadzu TOC-L Analyzer. To determine nitrogen content, samples were diluted by a factor of 300, then oxidized using 5 ml potassium persulphate (45 g -1) by heating to 160 °C for 40 minutes in a CEM MARS XPRESS microwave digestion system. Digestates were then analysed as nitrate-N using a San++ Automated Wet Chemistry Analyzer - SKALAR. The volume of the leachate collected and the measured concentration of C and N were combined to determine the C and N contained within the leachate as a proportion of total products C and N. Headspace gas samples were taken at day 0 and day 21. Samples were taken by injecting 20 ml of lab air into the headspace at the top of fermenter through the gas sampling port, flushing thoroughly, and then removing 20 ml of headspace gas and transferring it to Labco Exetainer® vial at 20 °C. Headspace gas samples were then analysed for CO2, CH4, and N2O concentrations on an Agilent 7890B Gas Chromatograph. The pH of fresh fermented solid products from each fermenter was measured on day 21 in a slurry of 1:10 solid:water using a HANNA HI-2550-02 Benchtop pH Meter and a representative sub-sample from each fermenter was freeze dried. Another sub-sample was weighed, dried at 105 °C, and re-weighed to determine the moisture content. All freeze-dried samples were milled using an agate ball mill (Fritsch P-5 Planetary Mill) at 300RPM for 90 seconds. Analysis for C and N was then completed by dry combustion using a C/N elemental analyser (Thermo Flash 2000 EA).

Institutions

• University of Reading

  England, Reading

Categories

Funders

• Biotechnology and Biological Sciences Research Council

  UK Research and Innovation

  Swindon

  Grant ID: BB/T008776/1

Licence