<![CDATA[Municipal solid waste (MSW) contains organic fractions that can be valorized into carbonaceous materials. This study evaluated the effect of phosphoric acid (H3PO4) concentration on the proximate characteristics of biochar derived from a defined mixture of banana peel, orange peel, and coconut husk. The feedstock was pyrolyzed at 250 °C for 3 h, and the resulting biochar was activated with nominal 20%, 25%, and 30% H3PO4 solutions at an impregnation ratio of 1:2 (w/v) for 24 h. Moisture content, volatile matter, ash content, and fixed carbon were determined using gravimetric methods, and treatment effects were evaluated statistically. The mean moisture contents were 8.55%, 8.00%, and 8.35% at 20%, 25%, and 30% H3PO4, respectively, compared with 11.30% for the unactivated biochar. Mean volatile matter decreased from 7.23% in the unactivated biochar to 4.64%, 4.43%, and 3.94%, respectively, while mean ash content decreased from 8.67% to 3.07%, 3.06%, and 3.04%. Mean fixed carbon increased from 72.80% in the unactivated biochar to 83.74%, 84.51%, and 84.68%. Statistical analysis showed a significant treatment effect on volatile matter (one-way ANOVA, p < 0.001) and fixed carbon (p = 0.038), but not on ash content (p = 0.559). Moisture content also did not differ significantly among the activated treatments (Kruskal–Wallis, p = 0.298). Tukey HSD showed that fixed carbon differed significantly only between the 20% and 30% H3PO4 treatments. The results indicate that H3PO4 concentration influenced the proximate composition of MSW-derived biochar, particularly volatile matter and fixed carbon. However, an optimum activation condition cannot be established from proximate characteristics alone.]]>
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