demonstration of biogas production using low moisture content

OBJECTIVES
The field phase of the experiment was conducted at West Texas A&M University’s Research Feedlot. Two
below ground "landfill" cells were constructed in Fall, 1998. The excavation was completed by Earthworks, Inc.
on September 23-25, 1998. The lower liner was installed in the two landfill-cell digesters on October 8-9, 1998.
Each cell measured 11 m x 11 m (34 ft x 34 ft) at ground level and was 2 m (6 ft) in depth with a 3 m x 3 m (10
ft x 10 ft) base. Each cell had a capacity of 91 m 3 (3,200 ft 3 ). A schematic of the landfill cells is shown in Figure
5.
Figure 5. Schematic of landfill-type biogas reacter.
Each cell was lined with an EPDM geosynthetic liner (Colorado Lining International, Parker, CO) on the bottom
and top (Figure 6). The first cell was filled with manure, saturated to 60% moisture content by weight, and
capped on February 12, 1999 (Figure 7). Initial volatile solids content of manure in the first cell was 32.0%. The
second cell was filled (60% moisture content by weight, initial VS=41.9%), and capped on January 5, 2000. A
gas collection apparatus was constructed of PVC pipe to collect gas samples at the top of each cell. Each cell
was equipped with a data logger (Starlogger Model 6004) and thermisters to monitor manure temperatures at
0.7 and 1.3 m above the bottom of each cell.
Each cell was capped by placing a single piece of EPDM geomembrane over the top of each cell and the
perimeter of the liner was buried. The gas was allowed to collect for several days, thus inflating the upper liner
into a dome. The volume of the dome was measured with surveying instruments.
To collect the biogas from the cells, a large plastic bag was attached to the exit port and was periodically tested
for methane content using a GT Land Surveyor portable methane analyzer (Gastech, Newark, CA).
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