Testing Soybean Peroxidase for Swine Manure Treatment

16 September 2014, at 12:00a.m.

Research at Iowa State University shows that the addition of soybean peroxidase to pig manure can reduce its environmental impacts in terms both of odours and harmful gases.

The control of odour, odorous volatile organic compounds (VOCs), hydrogen sulphide, ammonia and greenhouse gases (GHGs) emissions associated with commercial swine production is a critical need, according to Jacek Koziel of Iowa State University in a report for US Pork Checkoff.

Manure storage is the major source of gaseous emissions. This study aimed for the most comprehensive, to date, assessment of a manure additive for mitigation of gaseous emissions of all major compounds of interest from swine manure.

This study assessed topical application of manure additive treatment in controlled pilot and farm scales (soybean peroxidase (SBP); product code 516-IND; Bio-Research Products, Inc.).

This research builds on the previous published study where SBP product was mixed into manure and resulted in significant mitigation of odorous VOCs in lab scale.

In this research both pilot and farm scale testing of topical SBP treatment (and around 23.5:1 weight/weight mix of SBP:CaO2 catalyst) was conducted over about five months and about 1.5 months, respectively.

The effects of SBP dose and time were tested on pilot scale. The effects of time were tested on farm scale using the lowest SBP dose selected from the pilot study.

This work aimed at providing a comprehensive assessment of SBP treatment efficacy to mitigate emissions of odorous VOCs, odour, hydrogen sulphide, ammonia and GHGs, i.e. a set of target gases of concern to swine industry.

Results of farm scale testing were in general consistent with the results of pilot scale controlled tests.

Specifically, farm-scale testing of SBP resulted in mitigation of many important gases:

  • Ammonia emissions were reduced by 21.7 per cent and were statistically significant.
  • Hydrogen sulphide emissions were reduced by 79.7 per cent and were statistically significant.
  • Greenhouse gas emissions were reduced for nitrous oxide at 9.8 per cent and were not statistically significant. Both methane and carbon dioxide emissions were reduced by 6.2 per cent and 3.0 per cent, respectively, and were not statistically significant.
  • Sulphur VOCs emissions were significantly increased by 30.6 per cent for dimethyl disulphide. Effects on dimethyl trisulphide could not be assessed.
  • Volatile fatty acids emissions were significantly reduced by 37.2 per cent (butyric acid), 47.7 per cent (valeric acid) and 39.3 per cent (isovaleric acid).
  • Phenolics emissions were reduced by 14.4 per cent (p-cresol), 31.2 per cent (indole) and 43.5 per cent (skatole) and were statistically significant for indole and skatole.

The estimated cost of treatment (additives only) was estimated at $1.45 per marketed pig and $2.62 per marketed pig when the cost of labour was added.

Similarly, the estimated cost was $2.19 per pig space and year of the (additives only) and $3.95 when the cost of labour was included (2014 price benchmarking).

The cost estimate was at the lower range of comparable products tested for air quality mitigation ($0.01 to $18.2 per marketed pig).

Furthermore, the SBP treatment also resulted in a more comprehensive mitigation of a greater number of gases of concern for swine industry.

September 2014