TITLE:
Biogas Production from Various Typical Organic Wastes Generated in the Region of Cantabria (Spain): Methane Yields and Co-Digestion Tests
AUTHORS:
Carlos Rico, Rubén Diego, Agustín Valcarce, José Luis Rico
KEYWORDS:
Cheese Whey, Co-Digestion, Cocoa Shell, Dairy Sludge, Manure
JOURNAL NAME:
Smart Grid and Renewable Energy,
Vol.5 No.6,
June
6,
2014
ABSTRACT: Batch
trials were carried out to determine the methane potential yields of some
typical organic wastes generated in the region of Cantabria (Spain): cocoa
shell, cheese whey and sludges from dairy industry. Anaerobic co-digestion
trials of these wastes with dairy manure were also investigated in batch at
35℃. Cheese whey obtained similar methane yields than dairy manure, between
17.5 and 19.3 L CH4kg-1 cheese whey compared with 18.0 L
CH4kg-1 manure. Methane yields of various sludge samples
collected from wastewater treatment facilities of dairy industries were influenced
by its origin. Sludge samples from fat separation devices were the most
productive in terms of specific methane yields compared with biological sludge
from an aerobic reactor. Sludge samples from fat separator reached specific
methane productivities of 350 and 388 L CH4kg-1 VS (10.5
and 24.1 L CH4kg-1 sludge), whereas biological sludge
yielded 125 L CH4kg-1 VS (12.6 L CH4kg-1 sludge). The methane potential of sludge samples was influenced by solids
content. Cocoa shell resulted to be an interesting waste for anaerobic
digestion due to its high VS content, yielding 195 L CH4kg-1 cocoa shell. It is a waste that can considerably improve methane yields in anaerobic
co-digestion with dairy manure. However, at proportions of 10% cocoa shell, the
process was hindered by hydrolysis of particulate matter. Anaerobic digestion
at higher temperatures (thermophilic range) could be a better option for this
kind of waste. Co-digestion of 5% cocoa shell with 35% dairy sludge and 60%
dairy manure resulted in 80.5% higher methane production compared to anaerobic
digestion of dairy manure alone.