Dai Miyazaki

Development of methane energy recovery technology from food waste by anaerobic digestion

Akiyoshi Ohashi, Hideki Harada


A methane fermentation has been paid to attention in promoting making of the food waste
in the future a resource. However, a treatment of methane fermentation residue is so
expensive in actual, it doesn't become popular. Therefore, the methane fermentation reactor

with a little waste water treatment is required. In this study, new methane fermentation
reactor (CSTR) is developed, which solved the problem of the dry methane fermentation process
by using special agitator.


The reactor temperature is controlled 37�Ž and the raw material is mainly food waste from the
school cafeteria. When COD loading was reached at 8 kgCOD/m3/day , Ammonia nitrogen increased
from 4000mgNH4/kg-w.w. in 1 month , also free-ammonia increased from 300mgNH3/L to 1000mgNH3/L
because of food waste of TKN is around 5000-6000mgTKN/kg-w.w..So as to inhibit methane fermentation
for ammonia, we put rice straw and office paper mixed with food waste, which mean input only
carbon source, to diluted ammonia in the next phase. As a results, although inputting only
rice straw is not so effect on diluting ammonia, inputting food waste mixed with paper can decreased
ammonia conc. around 1000 mgNH4-N/kg-w.w. for 1 month.


And, since reactor�fs pH is 8.0-8.5 in all days, it supposed that ammonia changed ammonia
gas(Free-ammonia) for 10-20%. By calculation of ammonia gas removal which take account gas-liquid
equilibrium is 4% in the all days, but if liquid phase is aeration, more and more ammonia removal
is prospective.