Abstract In wood fuels, potassium is by far the most abundant aerosol forming component. Given this predominant role, a major contribution for meeting the tightened total particulate matter emission thresholds on European level could thus be expected by the introduction of an upper limit for potassium content in wood pellets. To evaluate options to introduce such an upper limit for the potassium content of wood pellets, an extensive pellet screening was performed in Germany covering 22 of the 46 ENplus certified wood pellet producers representing more than 50% of the current German wood pellet production of about 2 million t/year. This screening was accompanied by the compilation of wood pellet fuel data from different sources. In total, analysis data of 249 high quality wood pellet samples has been evaluated. Almost all pellet samples originated from European production whereof the majority were pellets from certified German pellet producers. The pellet screening revealed a very large variation in the potassium content of high quality wood pellets ranging from below detection limit to well above 1000 mg/kg d.b. The results also confirmed the predominant role of potassium among the aerosol forming elements potassium, sodium, lead and zinc in wood samples. Furthermore, the screening highlighted that the ash content is not sufficient to evaluate the potassium content of wood pellets. Analysis of selected raw materials from three different pellet producers revealed a strikingly large variation in the potassium content of the raw materials. Consequently, controlled adjustment of the potassium content in wood pellets in the production process would require dedicated mixtures of different raw materials and the limitation of the share of raw materials with particularly high potassium contents. In this way, the potassium content of wood pellets could be limited and this could contribute to the compliance with strict particulate emission thresholds for small scale combustion appliances. Prerequisite for such an approach would be a fast, simple and cheap possibility to determine the potassium content of raw materials for wood pellet production at the production sites and the incorporation of the potassium control in the quality assurance of the pellet production process. Consequently, wood pellets could be produced that facilitate compliance with particulate matter emission threshold without secondary emission reduction measures.

中文翻译：

---

市售木屑颗粒批次中钾和其他气溶胶形成元素的含量

摘要 在木材燃料中，钾是迄今为止最丰富的气溶胶形成成分。鉴于这种主要作用，因此可以通过引入木屑颗粒中钾含量的上限来满足欧洲水平上收紧的总颗粒物排放阈值的主要贡献。为了评估引入这种木屑颗粒钾含量上限的选项，在德国进行了广泛的颗粒筛选，覆盖了 46 家经过 ENplus 认证的木屑颗粒生产商中的 22 家，占当前德国木屑颗粒生产量的 50% 以上，约 2万吨/年。该筛选伴随着来自不同来源的木屑颗粒燃料数据的汇编。总共评估了 249 个高质量木屑颗粒样品的分析数据。几乎所有颗粒样品都来自欧洲生产，其中大部分是来自经过认证的德国颗粒生产商的颗粒。颗粒筛选显示优质木颗粒的钾含量变化很大，从低于检测限到远高于 1000 mg/kg db 结果还证实了钾在气溶胶形成元素钾、钠、铅和木材样品中的锌。此外，筛选强调灰分含量不足以评估木屑颗粒的钾含量。对来自三个不同颗粒生产商的选定原材料的分析显示，原材料的钾含量存在惊人的巨大差异。最后，在生产过程中控制调整木屑颗粒中的钾含量需要不同原材料的专用混合物，并限制钾含量特别高的原材料的份额。通过这种方式，木屑颗粒的钾含量可能会受到限制，这可能有助于遵守小型燃烧器具的严格颗粒排放阈值。这种方法的先决条件是一种快速、简单和廉价的可能性，可以在生产现场确定木屑颗粒生产原材料的钾含量，并将钾控制纳入颗粒生产过程的质量保证中。最后，