3.3.2. Waste paper-to-fuel pellets
Similar to the waste cooking oil-to-biodiesel process, GHG
emissions from the waste paper-to-fuel pellet process is mainly
due to the emission from the production of the electricity that is
used for this process because there is no direct GHG emission during
the conversion stage. The GHG emission from burning the pellets
is considered mostly as carbon neutral (biogenic CO2) (Sedjo,
2013), except for the part from the combustion of plastics in the
pellets. Since this option utilized paper waste generated on-site,
no transportation and packaging related emissions were considered.
As calculated from the previous section, producing 1 kWh
of electricity releases 881.59 g CO2-eq/kWh. Thus, the total energy
consumption for pellet production was estimated at 76,438 kWh/
yr and the corresponding emission would be 67.39 tonnes of
CO2-eq/yr. According to an EPA document (exhibit 17 in US EPA,
2010), the average emission factor for the combustion of plastics
was 2.8 tonnes of CO2-eq per tonne of plastics (2.54 tonnes of
CO2-eq per short ton of plastics). Therefore, the GHG emission of
58.10 tonnes of CO2-eq/yr was estimated from combusting
20.75 tonnes of plastic that were within the fuel pellets. So the
total GHG emission from the life cycle of fuel pellets was approximately
125.50 tonnes of CO2-eq. On the other hand, the replacement
of coal by the waste paper fuel pellets lead to a GHG
emission credit of 385.98 tonnes CO2-eq, when assuming the life
cycle GHG emission from coal production and combustion is
3.2 tonnes CO2-eq/tonne coal (Bartok, 2004). Therefore, the
net GHG reduction of pellet fuel was estimated to be 260.49
tonnes CO2-eq per year.