Schou, J.S., Gyldenkærne, S., Grant, R., Elmegaard, N., Palmgren, F. & Levin, G. 2006, Technical Report from NERI No. 575, 42 pp.

 

Summary:

 

The analyses demonstrate the environmental consequences of incineration of livestock manure in a specific catchment area where an unchanged animal production is presumed. The scenarios are carried out for the Vesthimmerland area, located in the north of the peninsula of Jutland (Denmark) where the agricultural production is characterised by a relatively intensive production of broilers and furred animals. It is assumed that half of the total production of manure from farms with broilers and mink is incinerated on incinaration plants on farm level and decentralised CHP plants. This corresponds to an incineration of manure from 1.951 DE (one animal unit corresponds to a production of 100 kg N per year) at which 219 tonnes N, 54 tonnes P and 118 tonnes K are removed, corresponding to 5 % N, 5.5 % P and 3 % K, respectively. The estimated environmental consequences are summarized in Table 19 and the results are commented below.

Assuming the effective N content of the incinerated manure is replaced with artificial fertiliser while not compensating for the removed P, it is estimated that the N leaching in the catchment area is reduced by 46.5 tonnes (approx. 2 %) while the P surplus is reduced from 200 tonnes to 146 tonnes (approx. 27 % reduction). Furthermore the incineration of manure will impact the emission of ammonia as the loss from storage and spreading is reduced. Thus there will be a reduction of ammonia emissions from storage facilities by 25.3 tonnes N while the reduction of emission from spreading is estimated to 17.2 tonnes N. All together a reduction of the ammonia emissions of 42.5 tonnes N is thus achieved.

Furthermore, analyses of additional deposition of gaseous N compounds, especially N2O, NO, NO2 and N2 from the air in the area close to an incineration plant have been carried out. The analyses presume that the amount of N emitted from incineration corresponds to the amount of N in manure. The analyses show that if the NOX concentration in the smoke is equal to the limit value set in the waste incineration directive (200 mg/m3) the deposition in the vincinity of the incineration plants will be relatively small (0.1 kg N with a chimney height of 25 m) compared with the general deposition of 10-20 kg N/ha. To the extent of which N is lost from storage as ammonia or N is accumulated in ash it will reduce the emissions of gaseous N compounds proportionally. It has not been possible to analyse these aspects further. The allocation of the gaseous N compounds of NOX and pure N will depend very much of the incineration technology and management.

 

Table A

Environmental consequences following from incineration of 50 % of livestock manure from broilers and mink in the catchment area Vesthimmerland.

 

 

Effect	Total	Per tonnes manure
Amount of incinerated manure	8,896 tonnes	-
Amount of dry solid matter in the incinerated manure	4,209 tonnes	-
Energy content in the incinerated manure	62 x 1012 J	-
Incinerated N amount	219 tonnes N	24.6 kg
Incinerated P amount	54 tonnes P	6.1 kg
Increased import of N artificial fertiliser	77.3 tonnes N	8.7 kg
Reduced ammonia emissions	42.5 tonnes N	7.2 kg
Reduced N leaching	49.5 tonnes N	5.6 kg
Reduced P surplus	54 tonnes P	6.1 kg
Reduced emission of greenhouse gases1)	2,434 ton CO2-eqv.	0.27 tonnes CO2-eqv.
Increased emission of NOXand elementary N2)	219 ton N; of this 11-22 ton NOX2)	24.6 kg N; of this 1.25 – 2.50 kg NOX
Maximal deposition of NOX 3)	0.1 kg N/ha	-

 

1) Effect on storage of carbon in soil is not included.

2) Calculated assuming that between 5 and 10 % of the total amount of carbon is emitted as NOX.

3) Provided that the limit values in the Incineration Directive are met.

 

In connection with the estimations of the changed nutrient loads the sensitivity of the effected recipients must be included. This implies that the affect will vary between localities, a fact that has not been elucidated in the present analysis.

The changed manure practise – as a consequence of the incineration – will also have consequences for the emissions of greenhouse gases, in the form of a reduction of the emission of methane and nitrous oxide and a reduced storage of CO2 in the soil. At present the effect on Denmark’s reduction commitment of greenhouse gases cannot be assessed as it depends on the time frame and whether Denmark chooses to use storage of C in farmland as a mean to fulfil its reduction commitment. Please note that the effects on the greenhouse gas emissions as a result of the manure not being spread in the fields as well as possible transport to incineration plants are not included in this analysis. Under these circumstances a reduction in the greenhouse gas emissions at 2,434 tonnes CO2 eqv. is achieved.

The possibility of using the ash, produced from incineration, for fertiliser purposes depends on a number of conditions. Provided the entire ash fraction is spread on farmland it is likely that the limit values for heavy metals defined in the Danish Sludge directive is exceeded. However, if it is possible to split the ash into different fractions, in which the P content is separated from the heavy metals, the P content can be used for fertilising purposes. Another and more costly option is to process and refine the ash into fertilisers. In both cases there may be a need for deposition of a part of the ash. This would actually act as a sink for heavy metals in agriculture, which may be an advantage in terms of environmental management, but this deposition will cost money.

Incineration of livestock manure must, today, be seen as a solution primarily feasible to environmental issues connected to the individual farm or catchment area. This could be e.g. realisation of demands posed in connection with an environmental approval or the fulfilment of the environmental goals for a water body in relation to the EU Water Framework Directive. The technology is, on the other hand, not expected to have a larger potential on a “here and now”-basis, because the share of the livestock manure applicable for incineration is small and the availability of energy production plants suitable for incineration of livestock manure is limited.

 

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