The total solids content of
manurewas taken from the OMAFRA NutrientManagement Software
[15] to be 8.4% for dairy cattle, and 28.4% for beef cattle. It is assumed
that dairy cattle produce 52 kg of manure per animal-day, and beef
cattle produce 34 kg of manure per animal-day with availabilities of
80% and 25%, respectively [27]. It was assumed that the volatile solids
available in the manures was 799 g per kilogram of total solids [19]. It
was also assumed that the efficiency of the AD system is 100%, and,
therefore, all of the volatile solids were consumed. The difference
between the total solids and the volatile solids is what is available for
fertilization use. Using the above values, the fertilization cost savings
by using the digestate is CAN$7.70 per animal-year for dairy farms and
CAN$5.32 per animal-year for beef farms.