Energy supply (Energiforsyning)

Heat and electricity is used in processes throughout the lifecycle of food products.


Electricity

Electricity is usually drawn from the public grid which is continuously supplied by a variety of power plants located in Denmark and neighboring countries. The sources of electricity vary during the day and over the year and the exact source of a given kWh electricity can not be identified. Changes in electricity consumption induced by the users influence the marginal electricity production technology whereas other production technologies remain unchanged. The marginal electricity production technologies are difficult to determine, but following Weidema (2003), natural gas fired power plants have been identified as the marginal electricity source of electricity in Denmark in the years to come. Hence, exchanges associated with marginal electricity production applied in this project are determined from emission factors derived from natural gas fired power plants (ETH 1996). Coal fired power plants are likely to be marginal electricity sources in Denmark as well (see Weidema 2003) and a sensitivity analysis with coal based electricity can be useful for detailed comparison of products or processes when impacts from electricity production are significant.

District heat is co-generated with electricity and environmental impacts associated with heat and electricity production at combined heat and power plants must be shared between the two products. It has been assumed 1) that district heat produced as a result of marginal electricity production will  be in excess in most cases and 2) that other factors than availability of excess heat from electricity production determines the size of the district heat network in the years to come. Therefore, exchanges associated with combined heat and electricity production is allocated entirely to the electricity.
 

Heat

Heat applied in Danish food industry is produced in many different kinds of furnaces with different fuels. In order to determine environmental impacts associated with food products produced in Denmark in general, a national mix of energy carriers specific for each sector has been applied (Danish NAMEA, 1999), see the table below.

 

 

 

 

 

 

 

LPG1,2)

Oil2)

Natural
gas2)

Hard
coal2)

District
heat3)

Slaughterhouses

1%

31%

65%

0%

3%

Fish industry

1%

16%

69%

13%

2%

Dairies

0%

15%

84%

0%

0%

Bread factories

8%

18%

68%

0%

6%

Sugar factories

0%

52%

0%

48%

0%

Wholesale

1%

21%

27%

0%

52%

Retail

1%

9%

30%

0%

60%


1) Bottled gas

2) Environmental impacts exchanges associated with heat production is based on ETH (1996).

3) About 75% of district heat distributed in Denmark is co-produced with electricity while 25% is produced at in pure district heat plants (LCA dansk el og kraftvarme, 2000). Marginal environmental exchanges associated with district heat co-produced with electricity are considered small because it is assumed (i) that the marginal heat produced at combined heat and power plants is usually in excess and (ii) that other factors than availability of excess heat from electricity production determines the size of the district heat network in the years to come. Eighty percent of district heat produced in pure district heat plants is produced by combusting biomass (LCA dansk el og kraftvarme, 2000). Thus, for the entire Danish district heat system it has been roughly estimated that environmental exchanges associated with demanding 1 MJ marginal district heat causes environmental impacts corresponding to 1/4 MJ heat produced at wood chips based district heat plants. The electricity consumption associated with heat distribution is estimated to 2.1 Wh/MJ (Veks, 2001).


 

References

Danish NAMEA (1999). National accounting matrices including environmental accounts. Statistics Denmark.

Weidema B (2003). Market information in life cycle assessments. Technical report, Danish Environmental Protection Agency (final draft). In press.

ETH (1996). Ökoinventare für Energisysteme (Teil I-VII) ETH Zurich (in Swiss). Data are available in SimaPro (in English). Updated data will be available at Ecoinvent Centre.

Veks (2001). Environmental declaration, Vestegnens Kraftvarmeselskab I/S.

Livscyklusvurdering af dansk el og kraftvarme (2000). Hovedrapport. In Danish.