The analyses of heavy and light metal concentrations in food
processing wastes revealed that the investigated materials were
suitable for biogas production. The content of most metallic elements
in the analyzed substrateswas within permissible limits. The
only exception was potassium which was observed in excessive
quantities in many waste samples. This problem can be solved
through co-digestion by bringing potassium levels closer to the
standard.
The evaluated food wastes constitute suitable substrates for
biogas production and contain mineral ions that enhance methane
formation.
The negative influence exerted by heavy metals on anaerobic
digestion is determined not only by their concentrations in the
substrate, but also by their chemical form, oxidation state, pH of the
feedstock and interactions with other compounds, including
antagonistic metals.
The concentrations of heavy and light metals in food wastes
should be monitored to guarantee the efficiency of biogas production.
Metal levels should also be analyzed in digestate which is
to be used as an agricultural fertilizer.