Page 100 - Materials Chemistry, Second Edition

86 A.-S. Nizami and I. M. Ismail

Environmental Advantages
Energy Advantages
-Odour elimination
- Pathogens reduction - High quality fuel production
- Sanitized compost production Biomethane from - Surplus heat and electricity
- Inrorganic fertilizer reduction Lignocellulosic production
- GHGs emission reduction Biomass - Energy imports reduction
- Carbon sequestration promotion - Decentralized power system
- Recycled water reuse promotion
- Groundwater and surface water - Fossil fuels reduction
resources protection

Economic Advantages
- Profit centres from transformation of
waste liabilities
- Valuing of Negative-value feedstocks
- Water consumption reduction
- Self-sufficiency increment

Fig. 3 Benefits of lignocellulosic biomethane production system

determined by considering different scenarios such as improved vehicle efficiency,
electricity from wind, use of wood chips for AD heating requirements and carbon
-1
sequestration of 0.6 t C ha -1 yr ; a minimum value for most European perma-
nent crops and grasslands. All of them results in GHG emission savings of up to
89.4 %. This achievement meets the EU directive 2009/28/EC requirements of
60 % GHG savings by 2018 (EC 2009). The crop production and AD process are
the main GHG emissions contributors in grass biomethane (Fig. 4). Among the
indirect GHG emissions, potassium and nitrogen fertilizers are the main contrib-
utors to agricultural emissions. The digester heating is the largest contributor in the
biomethane production process (Korres et al. 2011).
The wheat ethanol, rapeseed biodiesel, and sunflower biodiesel do not meet the
60 % GHG emission savings in comparison with grass biomethane (Fig. 5).
According to Thornley et al. (2009), issues of high nitrogen and pesticide
requirements are associated with rape seed biodiesel, which impacts the GHG
savings. Furthermore, the associated technology is poor. The low GHG savings
with wheat ethanol is due to the emission of N 2 O during cultivation and low
biofuel yields (Smith et al. 2005; Börjesson 2009). Similarly, sunflower biodiesel
only fulfills the conversion rate necessary to achieve 35 % GHG emission savings
from 30 % of arable land (Ragaglini et al. 2010). Nevertheless, there are envi-
ronmental benefits reported with sunflower biodiesel (Sanz-Requena et al. 2010).
The biomethane production on farms from manure, which is an easily accessible
substrate result in higher GHG emission savings (Korres et al. 2011). Nevertheless,