Spent coffee grounds (SCGs) have been extensively investigated as a feedstock to produce fuels, specialty chemicals and materials. Whilst a few reports have used cascade processes to generate several products from SCG, this work takes the novel approach of using integrated subcritical water extraction (SWE) and hydrothermal carbonisation (HTC) to derive three products: a bioactive extract, a protein isolate (SCG PI) and solid fuel. SWE and HTC processes were optimized producing an antioxidant rich extract, with the chlorogenic acid (CGA) content and antioxidant activity determined. The protein content was quantified via total amino acid analysis, giving the first SCG specific elemental nitrogen-to-protein conversion factor of 7.90. HTC was then performed on the residual solids from SWE, the protein extraction and the raw feedstock. This biorefinery approach gave higher quality products than previously reported in single product systems. For example, pretreatment reduced nitrogen in the hydrochar (N = 0.23% wt, HHV = 33.30 MJ/kg) relative to the control (3.03% wt, HHV = 31.31 MJ/kg). Limiting biorefinery processes to the pretreatment and HTC preferentially increased protein content (33.0% vs 16.9% wt) and yield (53.0% vs 23.9%) of the protein isolate, rendering a hydrochar with a higher yield and HHV compared with hydrochar derived following upstream SWE process (33.30 vs 26.92 MJ/kg, 16.3% vs 14.7%, respectively). This work goes towards the complete utilisation of SCGs within a biorefinery, highlighting the potential of subcritical water processing to produce commercially viable products across the value chain.

废咖啡渣（SCG）已被广泛研究用作生产燃料，特种化学品和原料的原料。尽管有一些报道使用级联工艺从SCG生成了多种产品，但这项工作采用了使用集成亚临界水萃取（SWE）和水热碳化（HTC）的新方法来衍生出三种产品：生物活性提取物，蛋白质分离物（SCG） PI）和固体燃料。优化了SWE和HTC工艺，生产了富含抗氧化剂的提取物，并确定了绿原酸（CGA）的含量和抗氧化剂的活性。通过总氨基酸分析对蛋白质含量进行定量，得出第一个SCG特定的元素氮-蛋白质转化因子为7.90。然后对来自SWE，蛋白质提取物和原始原料的残留固体进行HTC。这种生物精炼方法比以前在单一产品系统中报告的产品质量更高。例如，预处理减少了碳氢化合物中的氮（ 相对于对照（3.03％wt，HHV = 31.31 MJ / kg），N = 0.23％wt，HHV = 33.30 MJ / kg）。将生物精炼工艺限于预处理和HTC可以优先增加分离蛋白的蛋白质含量（33.0％vs 16.9％wt）和收率（53.0％vs 23.9％），与上游SWE后衍生的水炭相比，水炭具有更高的收率和HHV处理（33.30对26.92 MJ / kg，分别为16.3％和14.7％）。这项工作致力于在生物精炼厂中充分利用SCG，突出了亚临界水加工在整个价值链中生产商业上可行的产品的潜力。