Nowadays, manure treatment demand is increasing due to N
surplus in most of the European areas. De-localization of piggery farms to less concentrated areas, for full fertilizing nutrient recovering
by land spreading, is very difficult for several reasons: the
presence in the same areas of traditional crops and typical productions,
like in Italy the parmesan cheese, and also for other reasons
related to food quality and safety market strategies. One possible
solution is to export manure nutrients to less concentrated areas.
Therefore, technologies for manure valorisation and volume reduction
are needed. Solid/liquid separation of raw manure is a key
technology, since it can concentrate a high quantity of nutrients
in a small volume, making transportation off-farm easier and
cheaper. The remaining liquid fraction could be used on-farm as
fertilizer. Rather often, especially for large, intensive swine farms,
N surplus still remains after soli/liquid separation, therefore many
farmers will benefit with further treatment to reduce nitrogen
load. C/N ratio represents the main treatment bottle neck. Better
electron donors use is needed, therefore solid–liquid separation
as pre-treatment allows a more balanced C/N ratio in liquid fraction.
Among the available biological technologies, SBRs showed
the most promising performances. According to lab-scale as well
as full scale results, SBR allows up to 98% removal of COD, N and
P, and moreover it’s easy to be managed and controlled. Thus,
the proposed process can represent a new chance for solving environmental
problems generated by large industrial piggeries. Economic
evaluations indicated that the operative costs are
affordable by most pig farmers, with minor impact on meat price.
Electric energy costs, that represent the biggest cost item, can be
greatly reduced if the separated solids are anaerobically digested
for cogeneration. Co-digestion with energy crops and/or organic
wastes can even increase the profitability of the process. For these
reasons, in Italy, several integrated anaerobic/aerobic biological
treatment for intensive swine production are going to be constructed
and revamped in the near future.