Davor Kralik

Croatian Food Industry By-Products: Co-Digestion with Swine Manure vs. Use as Liquid Animal Feed

Food industry by-products such as spent brewers yeast and whey from cheese production are being amended with nutrients and used as a feed source in the Croatian swine sector. However, as interest in energy production and anaerobic digestion of animal manures has increased, co-digestion of these materials with manure could improve the economic viability of on-farm digesters. To determine the feasibility of this approach, consideration should be given to whether food industry by-products provide a better economic return as a low-cost animal feed or as an anaerobic digester feedstock. In addition, while slaughterhouse wastes are not used as an animal feed, this article also considers the use of this material as a co-digestion feedstock. The economic information and substrate selection presented in this article are based on by-products available to a swine farm in Croatia and production data from the facility while feeding with by-products. Biochemical methane potential (BMP) assays were used as a fast, inexpensive method to determine the potential methane production rates for the various substrates. Using BMPs, the potential methane production rates for various combinations of spent brewers yeast, whey, slaughterhouse waste, corn silage, and swine manure were also determined. Results of the BMP assays were used to compare the potential economic return of using the food wastes to produce methane in the digester to the value of these materials as feed ingredients for swine production. Based on live production data, liquid feeding of food industry by-products was calculated to provide a

Soybean Straw, Corn Stover and Sunflower Stalk as Possible Substrates for Biogas Production in Croatia: A Review

6.89 savings per finish pig produced over a 90-day period at the Croatian facility. Since the facility produces 14,000 finish pigs every 90 days, this represents a cost savings of

Anaerobic Digestion of Swine Manures with Different Types of Food Industry Waste

96,000 per turn, or over

Influence of zeolite application in pig breeding on biogas production

307,000 per year considering that the facility finishes 3.2 turns of pigs per year. Using cheese whey or spent brewers yeast as a co-substrate in the proposed swine manure digester has the potential to provide an additional income via electricity generation of

Mutual influence of protein and lipid feed content on European catfish (Silurus glanis) growth

26,000 and

EVALUATION OF VERMICOMPOSTED CATTLE MANURE

34,000 over a 90-day period, or

Comparison between biogas production from manure of laying heners and broilers.

83,000 and

Anaerobic digestion system selection for Croatian swine manures.

109,000 annually, respectively. These values were based on the value of the substrate, assuming that either a digester or liquid feeding system already existed. Based on the data, the economic return is better when the by-products are used as a feed ingredient. However, if the swine digester is amended with all available co-substrates, including whey, spent brewers yeast, slaughterhouse waste, and corn silage, the potential additional income is

CONVERSION OF ORGANIC MANURE INTO BIOGAS

168,000 per 90-day turn or

Sudan grass as an energy crop for biogas production.

538,000 per year. The data presented in this article include substrate characteristics, potential methane production normalized on the basis of mass of substrate volatile solids, estimated electricity generation potential, and economic data.