Short-term stored, long-term stored, and weathered biomass ashes (BAs) produced from eight biomass varieties were studied to define their composition, mineral carbonation, and CO₂ capture and storage (CCS) potential by a combination of methods. Most of these BAs are highly enriched in alkaline-earth and alkaline oxides, and the minerals responsible for CCS in them include carbonates such as calcite, kalicinite, and fairchildite, and to a lesser extent, butschliite and baylissite. These minerals are a result of reactions between alkaline-earth and alkaline oxyhydroxides in BA and flue CO₂ gas during biomass combustion and atmospheric CO₂ during BA storage and weathering. The mineral composition of the short-term stored, long-term stored, and weathered BAs is similar; however, there are increased proportions of carbonates and especially bicarbonates in the long-term stored BAs and particularly weathered BAs. The carbonation of BAs based on the measurement of CO₂ volatilization determined in fixed temperature ranges is approximately 1–27% (mean 11%) for short-term stored BAs, 2–33% (mean 18%) for long-term stored BAs, and 2–34% (mean 22%) for weathered BAs. Hence, biomass has some extra CCS potential because of sequestration of atmospheric CO₂ in BA, and the forthcoming industrial bioenergy production in a sustainable way can contribute for decreasing CO₂ emissions and can reduce the use of costly CCS technologies.

Part 1 of the present work elucidated some general considerations of inorganic matter in coal and determined and explained the relationships, namely statistically significant positive or negative correlations, for chemical characteristics. Complete data from chemical (proximate, ultimate and ash analyses) and mineral composition (major and minor minerals) of 37 coal samples worldwide were used for that purpose. The present Part 2 provides and explains the significant correlations for minerals of these coals. Then, some important relationships between the composition and rank and ash-fusion characteristics of the coals are described. Further, definitive mineralogical and geochemical indicators for genetic interpretations of coal formation are summarized. Finally, the potential implications of these relationships and indicators are discussed and certain new features that may be used as criteria for clarifying the coal properties and for predicting specific technological and environmental problems related to this fuel are also introduced and suggested.

The relationships between the chemical and mineral composition of 37 coal samples from Australia, Bulgaria, USA, Japan, Canada, South Africa, China, Spain, and Ukraine, which differ considerably in their geology, rank, age, ash yield, chemistry and mineralogy, have been investigated. For that purpose complete data from chemical (proximate, ultimate and ash analyses) and mineral composition (major and minor minerals) of these samples have been used. The study explains initially some general considerations of the inorganic matter in coal. Then, the work provides and elucidates the statistically significant positive or negative correlations of chemical characteristics of the coals studied. Further, different geochemical indicators for some genetic interpretations of coal formation are also provided and described. The correlations of minerals in coals, as well as the potential applications of relationships among chemical and mineral composition are described in Part 2 of the present work.

The mineralogy, elemental composition and modes of element occurrence in a vitrain lens from the western and peripheral part of the Vulche Pole coal deposit (Bulgaria) were studied. The total concentration of trace elements established in the lens is 12.7 % (ash basis) including 7.75 % Ge which is among the highest contents of the element reported until now. The low ash coal lens (7.8 % ash) contains a great variety of detrital and authigenic minerals. The group of detrital minerals and phases includes quartz, K-feldspars, plagioclases, biotite, amphibole, zircon, apatite (coarse crystalline), volcanic glass and native Au. The authigenic minerals are presented by pyrite, sphalerite, galena, gypsum, jarosite and anglesite. The identified minerals such as opal, cristobalite, kaolinite, illite, muscovite, Fe oxides-hydroxides, delafossite, apatite (fine crystalline), monazite, xenotime, gamagarite and stolzite could have a detrital and/orauthigenic origin. Despite extremely high (over Clarke) concentrations of such elements as Ge, U, Sb, Sm, V, Mo, Ce, Hf, Y, Yb, Zn, As, Tb and Zr, these elements demonstrate a strong association or dominant affinity with the organic matter. Some of the aforesaid elements occur as discrete minerals (Zn, Zr, Ce, Y, V, Hf) and as impurities in the minerals (Zn, As, V, Ge, Hf, U, Zr). However, the mineral matter is only a minor constituent in the lens and its contribution to the enrichment of these elements is not of great significance.