Fertiliser influence on alkali release during straw pyrolysis

Comparative studies of alkali release from wheat and oat straws cultivated in the laboratory with chloride-rich and sulphate-rich fertilisers are reported. The release of alkali during pyrolysis in the temperature range 25–1060°C is measured using the sensitive surface ionisation technique. Straw cultivated with a chloride-rich fertiliser releases two to four times more alkali than straw fertilised with a sulphate-rich fertiliser, and the release takes place at lower temperatures. The temperatures for maximum alkali release are ∼800°C for straw cultivated with a chloride-rich fertiliser, and ∼870°C for straw supplied with a sulphate-rich fertiliser. The samples were also subject to simple water leaching, and alkali was observed to be easily removed by leaching irrespective of fertiliser. Application of chloride-free fertilisers is concluded to be a simple and efficient way to reduce the alkali release from the fuels, and the method can easily be combined with other methods in order to improve fuel quality.