This study examined the dry matter losses and the greenhouse gas (GHG) concentrations within two short rotation coppice (SRC) willow wood chip storage heaps. One heap was built on a grassland area (East Midlands) and the other (Rothamsted) on a concrete hard standing. A series of 1- and 3-m probes were embedded in the heaps in order to retrieve gas samples for analysis, and pre-weighed net bags were positioned in the core of the heap to detect dry matter losses. The bagged samples showed dry matter losses of 18 and 19 % in the East Midlands and Rothamsted heaps after 210 and 97 days storage, respectively. The Rothamsted heap showed a whole-heap dry matter loss of 21 %. During this time, the wood chips dried from 54 to 39 % moisture content in the East Midlands heap and 50 to 43 % at Rothamsted. The results from analysing the whole Rothamsted heap indicated an overall loss of 1.5 GJ per tonne stored, although measurements from bagged samples in the core suggested that the chips dried sufficiently to have a minimal energy loss from storage. The process of mixing the heap, however, led to incorporation of wet outer layers and hence the average moisture content was higher in an average sample of chip. After establishment of the heaps, the temperature rose rapidly and this correlated with a peak in carbon dioxide (CO₂) concentration within the heap. A peak in methane (CH₄) concentration was also detected in both heaps, though more noticeably in the East Midlands heap after around 55 days. In both instances, the peak CH₄ concentration occurred as CO₂ concentrations dropped, suggesting that after an active period of aerobic decomposition in the first 2 months of storage, the conditions in the heap became anaerobic. The results from this study suggest that outside wood chip storage is not an efficient method of storing biomass, though this may be location-specific as there are some studies showing lower dry matter losses. It is necessary to explore other methods of harvesting SRC to minimise losses and optimise land use efficiency. Further research is required to detect whether there are fugitive emissions of CH₄ from wood chip heaps, as this will compromise the net GHG savings from utilising the biomass stored in this way.

中文翻译：

---

短周转矮林柳片外部储存的干物质损失和温室气体排放。


本研究检查了两个短轮伐期矮林 (SRC) 柳树木片储存堆内的干物质损失和温室气体 (GHG) 浓度。一堆建在草原地区（东米德兰），另一堆（洛桑）建在坚硬的混凝土立柱上。在堆中嵌入一系列 1 米和 3 米的探针，以便检索气体样本进行分析，并将预先称重的网袋放置在堆的核心以检测干物质损失。袋装样品在储存 210 天和 97 天后，东米德兰和 Rothamsted 堆中的干物质损失分别为 18% 和 19%。 Rothamsted 堆显示全堆干物质损失为 21%。在此期间，东米德兰兹堆中的木片含水量从 54% 干燥至 39%，洛桑斯特德干燥站的含水量从 50% 降至 43%。分析整个 Rothamsted 堆的结果表明，每吨储存的总能量损失为 1.5 GJ，尽管对岩心袋装样品的测量表明，碎片已充分干燥，储存过程中的能量损失最小。然而，混合堆的过程导致了湿外层的结合，因此平均水分含量在木片的平均样品中较高。堆建立后，温度迅速升高，这与堆内二氧化碳 (CO ₂ ) 浓度的峰值相关。在两个堆中也检测到甲烷 (CH ₄ ) 浓度峰值，但在东米德兰堆中在大约 55 天后更为明显。在这两种情况下，当CO ₂浓度下降时，CH ₄浓度达到峰值，这表明在储存的前两个月的需氧分解活跃期之后，堆中的条件变得厌氧。 这项研究的结果表明，外部木片储存并不是储存生物质的有效方法，尽管这可能是针对特定地点的，因为有一些研究表明干物质损失较低。有必要探索其他收获SRC的方法，以尽量减少损失并优化土地利用效率。需要进一步研究来检测木片堆是否存在 CH ₄逃逸排放，因为这将损害利用以这种方式储存的生物质所节省的净温室气体排放量。