Briquetting and carbonization of naturally grown algae biomass for low-cost fuel and activated carbon production

This study reports the briquetting and carbonization processes of naturally grown algae biomass collected from regional lakes. After drying them in air and chopping them into small pieces (∼2.5 × 2.5 cm), three different briquetting pressures (e.g., 2, 3, and 5 tons/cm2) were applied to form algae briquettes with 3-5% moisture content. Three major investigations were performed on the prepared samples. The first test was to investigate the briquettes' handleability, in which the algae briquettes were dropped 100 times from a height of 1.524 m to resemble a handling mechanism. The second test was conducted on the samples to resolve the residual strength of the briquettes before and after the carbonization process at 800 °C. Ignition points of the algae briquettes were reviewed in the third analysis. Test results showed that briquettes under 2, 3, and 5 tons/cm2 of pressure had density values of 1303, 1423, and 1553 kg/m3, respectively. Drop tests demonstrated that the weight contractions of the briquettes were reduced from 10.2% to 2.1%, when the pressure was intensified from 2 to 5 tons. Ignition temperatures for the non-carbonized briquettes under 2, 3, and 5 tons/cm2 were 492, 510, and 520 °C, respectively; however, after carbonization, these temperatures were reduced to 474, 487, and 492 °C, respectively. Compression strength tests for the non-carbonized briquettes under 2, 3, and 5 tons/cm2 resulted in 22.1, 29.2, and 33.5 MPa, respectively. These test outcomes can be suitable for future guidance of an algae-based biomass and fuel system for reducing environmental impacts.