Multi-element combined methods increase the reliability of emission factor measurement

In te r n a tio n a l A m m o n ia C o n fe r e n c e in A g r ic u ltu r e , M a r c h 2 0 0 7

Multi-element combined methods increas e the reliability of

emis

sion factor measurement

M. Has s ouna

, P. Robin

, J.-M. Paillat

1

INR A C IR AD, Agrocampus R ennes, UMR 1069, S ols, Agronomie, S patialisation, F-35000 R ennes

2

INR A, UMR 1079 S ystèmes d'E levage Nutrition Animale et Humaine, F-35590 S aint Gilles

UMR Sol Agronomie Spatialisation

This work was supported financially by the GIS “Porcherie Verte”

Introduction

Inventories or Life Cycle Assessment use emission factors for livestock buildings but their results are sensible to the variation range of the emission factors. At the farm scale, technique improvement needs to quantify their effect on the emission factors.

Present variability depends either on system characterisation (i.e. intra-class variability) or on measuring method (gradient

measurement, air flow rate measurement, time extrapolation).

Therefore, there is a need to develop robust methods that will lead to quantify the accuracy of emission factor estimates.

In the case of livestock buildings, the measurement period should take several months, it should be adapted to both short-term and mid-term variability of the climate and the farmer practices, and it should allow simplifications for emission certification.

Materials

and Methods

The measuring equipment (Fig. 1) associates devices allowing the use of methods considered as reference ones (tracing gas), completed by devices allowing the use of simplified methods (indirect ventilation estimates) or the cheapest method: default of mass balance.

Each method has its own pros and cons: technical advantages, assumption validity, price.

Fig. 1: MECM measuring system: the tracer gas method is compared to indirect ventilation measurements and to the default of mass balance (H₂O, C, N); it allows a two-level simplification.

Res ults

Dis cus s ion and conclus ion

• Multi-element approach (H₂O, C, N, P, K) allows the verification of

the estimates and the simplification of the reference method, because the various elements have contrasted behaviours.

• Combined methods (“continuous flow” and “decay rate” tracer methods; indirect ventilation measurement; mass balance of the effluent) make it easier to check the observations against realistic values of heat production within the building (instantaneous observations) or realistic values of gaseous losses (mass losses after some weeks or months).

• Gas concentration measurements can lead to both simplified instantaneous estimates, when combined with T-HR measurements, and simplified integrated estimates, when combined with effluent mass balance (see Hassouna et al, same conference).

• Increasing the redundancy of the data set increases the possibilities to reduce the uncertainty in the emission factor estimates.

Fig. 3: air flow rate estimates show the sensitivity of the methods to the given dose and the observed concentration variability.

Fig. 2: Kinetics of SF₆ -tracer concentrations:

several successive measurements on the

same channel and at least two channels outside and inside are necessary to

evaluate the measurement accuracy.

Meteorological station

(detailed and continuous climate characterisation)

+ T-HR (sensor+logger: minimum climate

characterisation)

Mixing system (homogeneity of gas concentrations and tracer

injection)

T-HR (sensor+logger: detailed or

minimum climate characterisation)

Effluent (sampling and

weighing + information on food, water, and straw inputs, and on animals)

Gas analyser

coupled with sampling and dosing multiplexer and computer

Fig. 4: heat production (total, sensible or latent) also used in indirect

ventilation estimates, reveals unrealistic air flow rate estimates.

Mass balance examination (after temporal extrapolation)

• P and K excreted should be found in the effluent (correct sampling);

• H₂O emitted should be slightly higher than lost water (metabolic

water);

• CO₂+CH₄ emitted should be slightly less than lost C (VOC);

• N₂O+NH₃ emitted should be less than lost N (N₂).

< < < < < < < < < ðSJ24/01/ êSD24/01/ äS>24/01/ ÝS724/01/ [S F6 ] m g /m 3

continuous flow method

decay rate method

0 100 200 300 400 500 600 700 800 22/01/04 23/01/04 24/01/04 25/01/04 26/01/04

mean theoretical total heat production of pigs (CIGR, 1984) observed total heat production (pigs + litter)

total heat production (W/pig)

?? _?? 0 10000 20000 30000 40000 50000 60000 24/01/04 00:00 24/01/04 04:48 24/01/04 09:36 24/01/04 14:24 24/01/04 19:12 25/01/04 00:00 [a ir f lo w r a te ] m 3 /h "decay rate" estimates (lines) and hourly median (squares) "continuous flow" estimates (lines) and hourly median