CO2 Emission Analysis
Current Heating system
In order to assess the CO2 emission reduction associated to the new heating system, an analysis of the system currently in place has been undertaken. The following figures present a breakdown of the different energy sources used to meet Barony’s yearly3 requirements and the related CO2 emissions.
The values are based on the following CO2 pollution figures1:
UK grid electricity: 160g/MJ (electric)
Oil: 120 g/MJ
LPG: 100 g/MJ
Proposed Heating System
The proposed heating system is assumed to work as follows:
-when there is a heating load, the biomass boiler provides both heat and
hot water and the oil boiler acts as a back-up heating source in case
of extreme weather conditions
-when there is no heating load (June, July, August), the oil boiler provides
the energy for hot water
• Oil-boiler contribution
Based on a 12kW average hot water consumption over the summer months (this
is probably a conservative value given that the occupancy is lower during
the summer), the amount of energy supplied by the oil boiler is:
E=12E3*3600*24*90=9.33E10J=9.33E4 MJ
In addition to this, we must take into account the CO2 released by the
oil-boiler when it backs up the biomass boiler in case of extreme weather
conditions. This amount of energy was estimated to be around 9.75E10J
= 9.75E4 MJ (based on a 330kW biomass boiler and on the climatic files
of the Dumfries region).
Consequently the amount of CO2 emitted is:
(9.33E4+9.75E4)*0.12=2.29E4 kg = 22.9 tons
• Biomass boiler contribution
This means that
4.261E12-1.908E11 = 4.07E12 J = 4.07E6 MJ
will be supplied by the biomass boiler (where 4.261E12 is the overall
yearly heating and hot water energy consumption).
The amount of CO2 released by the biomass boiler will strongly depend
on the distance travelled by the delivery lorry. The following values
will be used in the calculations:
mCO2 = 33 + 0.27*x (kg/ODT wood)2
33 kg is the amount of CO2 released in order to collect and process one
oven dry ton (ODT) of woodchips and 0.27kg is the amount of CO2 released
by transporting one oven dry ton of woodchip over a kilometre. No CO2
is added for the combustion of the woodchips since it is assumed that
trees are being grown elsewhere in Scotland to replace the ones that have
been felled to provide the woodchips.
Considering that the furthest supply distance between Barony College and
a supplier within the “Dumfries and Galloway” region is 130km,
the amount of CO2 released per oven dry ton of woodchips is:
mCO2 = 33 + 0.27*130=68.1 kg/ODT
The calorific value of an oven dry ton of woodchips is: 19.5 GJ/ODT
The mass of CO2 released to cover the energy needs of the Barony college
is therefore:
mCO2 = 4.07E3/19.5*68.1=1.421E4 kg = 14.2 tons
Old and Proposed System Comparison
The amount of CO2 released by the proposed system is 15 times smaller than that of the previous system. Even though the biomass boiler provides the bulk of the energy, the amount of CO2 released by the oil boiler is greater than what is released by the woodchip system.
References
(1)Scottish executive website
(2) The royal commission of environmental pollution
(3) Barony college’s 2006 energy bills
Clarify
Standpoint of Organisation |
Quantify
Demand Requirements |
Assess
Potential Biomass Supply within Local Area |
Match
Demand & Fuel Supply to Available/Suitable Technologies |
Check
Relevant Legislation |
Apply
for Funding |