## 4 Results
### Estimating Grassland Sequestration  
[PERSON] _et al._[15] provide an estimate of carbon sequestered within an area of productive Irish grassland (Table 2). This estimate followed a farm survey (which relates to two farmed grassland areas in County Cork: farms A and B) and represents the amount of carbon retained by a pasture-based farm area when the movement of embodied carbon through the farm boundary is taken into account. However, the area examined in [PERSON] _et al._[15] is not a drained organic/peaty soil. In order to compensate for the decomposition of organic matter, the estimate of NEE was replaced by the net emission from such soils [28]. The methane oxidation rate was replaced by a value which represents an average of grassland and bog areas, taken from [PERSON] _et al._[32]. These estimates were applied to the pasture area provided by the Central Statistics Organization (CSO). The area of organic soils under pasture in 2007 was taken from [28]. This value was subtracted from the total pasture area and the net carbon balance of a peaty grassland area (\(-0.25\) t C/ha/yr) was applied. Averages of the values for farm A and B were used to estimate the other categories within the organic farm. As this value does not include the effect of outdoor respiration, the value for animal respiration generated for farm B reflects the entire year as opposed to the period indoors. Based on the herd distribution and respiration rates published in [15], it was suggested that cattle respire 0.53 and 0.58 t C/ha/yr during outdoor periods for farms A and B, respectively. This value was \begin{table}
\begin{tabular}{|l|l|l|l|} \hline  & **Farm A** & **Farm B** & **Organic (estimated)** \\ \hline
**Carbon inputs** & **t C/ha/yr** & \\ \hline Net ecosystem (NEE) & 2.9 & 2.9 & \(-0.25\) \\ \hline Concentrates & 0.4 & 0.68 & 0.54 \\ \hline CH\({}_{4}\) oxidation & 0.0015 & 0.0015 & 0.0028 \\ \hline
**Inputs sub Total** & 3.3015 & 3.5815 & 0.29282 \\ \hline
**Carbon outputs** & & & \\ \hline Milk & \(-0.21\) & \(-0.31\) & \(-0.26\) \\ \hline Meat & \(-0.02\) & \(-0.02\) & \(-0.02\) \\ \hline Enteric fermentation & \(-0.11\) & \(-0.12\) & \(-0.115\) \\ \hline CH\({}_{4}\)—Dung in farmyard & \(-0.001\) & \(-0.001\) & \(-0.001\) \\ \hline CH\({}_{4}\)—Dung in field & \(-0.0005\) & \(-0.0005\) & \(-0.0005\) \\ \hline CH\({}_{4}\)–Slurry spreading & \(-0.08\) & \(-0.06\) & \(-0.07\) \\ \hline DOC (in stream) & \(-0.1\) & \(-0.1\) & \(-0.1\) \\ \hline CH\({}_{4}\)–Slurry in storage & \(-0.0001\) & \(-0.0001\) & \(-0.0001\) \\ \hline Animal respiration & \(-0.73\) & \(-0.82\) & \(-1.3281\) \\ \hline
**Outputs Sub Total** & \(-1.2516\) & \(-1.4316\) & \(-1.3416\) \\ \hline
**Net balance** & **2.0499** & **2.1499** & **\(-\)1.6018** \\ \hline \end{tabular}
\end{table} 
Table 2: Farm-based carbon sequestration estimate relating to two farmed grassland areas in County Cork, Ireland: farms A and B, taken from [15] and augmented. averaged and added from the existing NEE and it is assumed to cancel out the reduction of NEE due to animal respiration while grazing. The resultant values are hoped to approximate the sequestration capacity of natural grassland. A modified NEE value should be viewed with a caveat--as there is still possibility that extraneous carbon emissions (such as those relating to fossil fuel combustion) are detected by eddy covariance equipment, although the pasture site was a considerable distance from the main farm. The change in animal diet associated with indoor housing (such as the use of dried food) will, due to changes in digestibility, more readily alter the enteric fermentation estimate; however this has presumably been taken into account in [15]. Similarly, the distribution of different animal types, time outdoors, and herd size is explicitly detailed in [15] and corresponds with conventional practices of Irish pasture management. Nevertheless, the assumption that indoor respiration rates are suitable proxies for outdoor estimates may be questioned.