# Effect of Distillery Spent Wash Utilization on Maize Silage Fermentation and In Vitro Methane Production

## TL;DR

This study shows that using a by-product from the alcohol industry in corn silage can improve fermentation and reduce methane production in livestock digestion.

## Contribution

The novel use of distillery spent wash as a feed additive to improve silage fermentation and reduce methane emissions is presented.

## Key findings

- Adding distillery spent wash increased lactic acid production and improved silage fermentation quality.
- Treated silage showed reduced methane production in simulated in vitro fermentation.
- DSW increased dominance of Lactiplantibacillus bacteria while decreasing acetic acid levels.

## Abstract

The animal husbandry industry produces large amounts of methane, a gas that contributes to global warming. Scientists are seeking practical methods to reduce the methane released during digestion in ruminants such as cattle. In this study, we explored whether a by-product of the alcohol industry—distillery spent wash—can be used as a natural additive in corn silage. We found that adding small amounts of this liquid promoted the growth of beneficial lactic acid bacteria, thereby improving fermentation quality while lowering the levels of undesirable acids. The treated silage also produced slightly less methane during simulated in vitro fermentation in the laboratory. This suggests that distillery spent wash could serve as a low-cost, environmentally friendly feed additive that both improves feed quality and helps reduce greenhouse gas emissions from livestock. At the same time, reusing this industrial by-product offers a sustainable way to reduce waste from the brewing industry.

The animal husbandry industry is a major source of agricultural greenhouse gas emissions, and methods to reduce methane production from livestock during rumen fermentation are an important research issue. Distillery spent wash (DSW) is a by-product of the brewing industry, and to our knowledge, its application in feed processing has rarely been reported. This work investigated the effect of using DSW as an additive on silage fermentation and in vitro methane production. A small-scale silage production system for whole-plant maize was applied, and maize was treated without (control) and with DSW (G2, 10 mL·kg−1 fresh matter (FM); G4, 20 mL·kg−1 fresh matter). After 60 days of ensiling, the pH value of G2- and G4-treated whole-plant maize was reduced (p < 0.05), while lactic acid production was significantly enhanced to 3.40% DM for G2 and to 3.43% DM for G4, effectively improving silage fermentation. In fact, the addition of DSW shifted the bacterial community structure in whole-plant maize silage, significantly increasing the dominance of Lactiplantibacillus from 10.1% (CK) to 74.1% (G2) and 62.5% (G4) and thereby decreasing the diversity indices of silage samples. However, DSW application increased the ammonia-N levels in silage by 135.29–147.06% compared with the control. Importantly, there was a reduction of 0.70 and 0.55 percentage units in CK for G2 and G4, respectively, which represent 57.6% and 44.0% reductions in the acetic acid concentration, respectively, which were accompanied by a trend of decreasing methane production and Methanobrevibacter abundance. In conclusion, DSW exhibits potential for enhancing lactic acid fermentation by increasing Lactiplantibacillus and for inhibiting in vitro rumen methane production by promoting Methanobrevibacter dominance.