Methane production from feather waste pretreated with Ca(OH)₂: Process development and economical analysis

This study investigated the industrial application
of feather waste as a substrate for anaerobic digestion. Feather
was pretreated with 0–0.2 Ca(OH)2 g/g TSfeather (total solids
of feathers) for 30–120 min at 100–120 C, in order to
increase the digestibility, and to enhance the methane yield in
a subsequent digestion at 55 C. Based on the results of the
batch digestion, an industrial process was developed, which
can achieve 0.40 Nm3/kgVSfeather (volatile solids of feathers)
methane yield fromthe pretreated feathers, while it fulfills the
animal by-product hygenization requirements as well. This
base case of the industrial pretreatment process was designed
using SuperPro Designer for utilizing 2,500 tons of feathers
per year, which is the waste stream from an average slaughterhouse
with a capacity of 60,000 broilers per day. The
production cost of the methane is estimated to be 0.475 EUR/
Nm3, while the investments on the pretreatment unit requires
0.97 million EUR as total capital investment, and 0.25 million
EUR/year for operating cost. However, the process is
sensitive to the plant capacity. Changing the plant capacity
from 625 to 10,000 tons of feather per year, results in
reducing the biogas production cost from 1.177 to
0.203 EUR/Nm3. In addition, sensitivity analysis was performedon
the base case to investigate the effect of the value of
the incoming feather on the overall process profitability. The
results showed that the proposed investment could be considered
as being financially viable in the case of production of upgraded biomethane even without the current gate fee
system.