Methane production from maize in Finland – Screening for different maize varieties and plant parts

The objective of the study was to determine how the harvest time and maize variety (12 varieties) affects the methane yield and dry matter yield per hectare in southern Finland (Piikkiö) and in Central Finland (Laukaa). The specific methane yields and methane yields per hectare were also determined for different plant parts (stem, leaves and cobs). The methane yield per hectare varied from 2130 to 9170 m3 ha−1. The methane yields per hectare were ∼50% lower in Laukaa than in Piikkiö due to a shorter growing season and lower total solid (TS) yields. TS yields were on average 16.7 and 15.5 Mg ha−1 in Piikkiö and 8.7 and 6.8 Mg ha−1 in Laukaa in 2007 and 2008, respectively. The specific methane yields varied from 366 to 491 dm3 kg−1 volatile solid (VS) in 2007 and from 296 to 373 dm3 kg−1 VS in 2008. The harvest time and sowing time did not affect the specific methane yields (p > 0.05). Whole maize crops produced more methane in batch assays than stem (372 dm3 kg−1 VS), leaves (334 dm3 kg−1 VS) and cobs (421 dm3 kg−1 VS) alone, and also the specific methane yields per hectare were higher than the methane yield per hectare calculated for the various plant parts. Maize cultivation for biogas production appears to be feasible only in southern Finland.