lower moisture and ash contents and volatile matter, and higher fixed carbon correspond to higher calorific value of the coal. So, lignite has lower calorific value than sub-bituminous and bituminous coal, and (sub) bituminous coal has lower calorific value than anthracite. Normally, only the organic parts of the coal are burned during the combustion process, whereas carbon dioxide and water vapor are produced as by-products. The inorganic parts of coal usually do not burn but stay in the ash as by-products.

**Table A2.5** : Gross calorific values (kcal/kg) of commonly used fuels for brick making process in India and Nepal

|Fuel type|(Weyant et al.,<br>2016)|(Kumar<br>and<br>Maithel, 2016)|(PSCST,<br>2015)|(SMSEE,<br>2017)|(Prajapati et al.,<br>2019)|
|---|---|---|---|---|---|
|Coal|6,483 (6,254)<sup>a</sup>|4,000 – 7,000|-|4,000 - 5,500<br>a|-|
|Wood chips|-|3,500 – 4,500|-|-|-|
|Sawdust|4,000<sup>a</sup>|3,500 – 4,500|-|-|2,961<sup>e</sup>|
|Coffee husk|-|4,300 – 4,500|-|-|-|
|Mustard stalk|4,007|-|3,985|-|-|
|Biomass briquettes<sup>b</sup><br>|-|-|3,155<sup>c</sup>|-|3,277<sup>e</sup>|
|Paper plant ash<sup>d</sup>|704|-|-|-|-|
|Iron plant ash<sup>d</sup>|2,789|-|-|-|-|
|Bagasse|3,166|-|-|-|-|
|Coal ash<sup>d</sup>|2,906|-|-|-|-|
|Paddy straw<sup>d</sup>|-|-|3,386|3,403 - 3,471<br>a|-|
|Cow dung<sup>d</sup>|-|-|2,831|-|-|

Notes: a Nepal-specific value. b Biomass pellets and briquettes are environmentally friendly alternative fuels to coal in brick making. Other advantages include higher calorific value when pelletized these biomass fuels and the creation of a market. Pellets and briquettes are produced by compacting loose biomass such as sawdust, crop waste, tree branches, rice husk, straw, and bagasse. The calorific value of high-quality briquettes ranges between 18 and 24 MJ/kg (BiofuelCircle, 2022).<sup>c</sup> Paddy and mustard ratio of 50:50.

d Mainly used as internal fuels during clay preparation and molding. e Reported values are for Nepal and expressed in MJ/kg. We use the conversion factor of 1MJ = 239 kcal. Sawdust is a mixture of 70% sawdust and 30% wood chips. Biomass briquettes (pellets) are sawdust pellets imported from India. The average cost of sawdust is NRs 10 per kg and the pellets made from sawdust and imported from India are NRs 26 per kg.

Most of the coal consumed in Nepal is imported from India, but some is also imported from as far as Indonesia, the United States, South Africa, and Australia. A small quantity of low-quality lignite is produced domestically in the Lumbini province (Dang and Palpa districts) of Nepal. In the past 12 years (2010-2021), about 98,000 tons of lignite have been excavated (DOMG, 2022). This is equivalent to an average of 8,128 tons per year and it is less than 1% of total coal imported each year (WECS, 2022). Most of these imported coals are relatively low-rank thermal (steam) coal mainly used for firing clay bricks. The gross calorific of imported coal varies widely from a low value of 4,000 kcal/kg (Indian coal) to a high value of 5,500 kcal/kg (Indonesian coal) (SMSEE, 2017).<sup>22</sup> The gross calorific values of commonly used fuels for firing clay bricks in India and

> 22 A local coal supplier and distributor (AKTraders) located in Kapilvastu district reported gross calorific value of 7,300 kcal/kg for American coal, 1,330 - 6,200 kcal/kg for Indian coal, and 4,200 kcal/kg for Indonesia. This information cited from https://nepalcoal.com/ and extracted on October 20, 2023.

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