Key factors influencing the potential of catch crops for methane production

Abstract

Catch crops are grown in crop rotation primarily for soil stabilization. The excess biomass of catch crops was investigated for its potential as feedstock for biogas production. Ten variables affecting catch crop growth and methane potential were evaluated. Field trials and methane potential were studied for 14 different catch crops species, with 19 samples harvested in 2010 and 36 harvested in 2011. Principal component analysis was applied to the data to identify the variables characterizing the potential for the different catch crops species for methane production. Two principal components explained up to 84.6% and 71.6% of the total variation for 2010 and 2011 samples, respectively. Specific methane yield, climate conditions (rainfall and temperature) and total nitrogen in the biomass were the variables classifying the different catch crops. Catch crops in the Brassicaceae and Graminaceae botanical families showed the highest methane yield. This study demonstrates the importance of the crop species when choosing a suitable catch crop for biogas production.

Biogas production from catch crops: Increased yield by combined harvest of catch crops and straw and preservation by ensiling

“…The combination of tall fescue and straw (T2) achieved the highest methane yield of 223 m 3 t À1 on VS basis, b i o m a s s a n d b i o e n e r g y 7 9 ( 2 0 1 5 ) 3 e1 1 representing a 51% increase if compared to straw alone (C). Specific methane yields of the catch crop and straw blends were, on the other hand, up to 2.9 times lower than those obtained for the specific catch crops in previous studies [3]. This is due to the high proportion of straw in the mixtures, which is also reflected in the similar composition of the mixture of perennial ryegrass and wheat straw (2B) compared to wheat straw alone (2D, 2E, 2F) ( Table 3).…”

“…These production costs were estimated after different scenarios both for pure catch crops (Fig. 1), based on the data reported by Molinuevo-Salces et al [3], and blends of catch crop and wheat straw (Fig. 2), based on the data from the present study.…”

“…In general, catch crops provide most often biomass yields as TS below 1 t ha À1 y À1 . However, biomass yields as TS of more than 3 t ha À1 y À1 were obtained in some cases [3]. The biomass yield of a specific catch crop depends on several parameters.…”

“…Furthermore, catch crops have recently become of major interest as a potential biomass resource for biogas plants in order to achieve the new target for Denmark of treating 40% of the total manure in biogas plants until 2020. The feasibility of using different catch crop species as cosubstrate for manure-based biogas plants in Denmark has recently been studied [2,3]. The methane yield that can be obtained per hectare of catch crop per year (m 3 ha À1 y À1 ), which is the product of the biomass yield as volatile solids (VS) per hectare of catch crop per year (t ha À1 y À1 ) and the specific methane yield on VS of the catch crop (m 3 t À1 ), is the main parameter determining the economic viability of using catch crops as substrate for anaerobic digestion [4].…”

“…These parameters determine the specific methane yield [6e8]. This specific methane yield on VS for catch crops is in the range 213e442 m 3 t À1 y À1 [3]. The volume of biogas that can be achieved per hectare of catch crop is rather determined by the biomass yield of catch crop per hectare than by the specific methane yield of the catch crop biomass [2].…”