Influence of different storage conditions on quality characteristics of seed material from semi‐natural grassland

Neither methodology nor guidelines are available for defining quality characteristics and storage conditions of seed material harvested from semi‐natural grassland. Seeds from an Arrhenatherion meadow were harvested via on‐site threshing and seed stripping. After determination of purity, thousand seed weight and pre‐tests in a phytotron, germination‐capacity trials were carried out in a greenhouse. The harvested seed material was stored for up to 3 years under different conditions: (i) room temperature 18–23°C, (ii) cooling chamber (2–5°C with 40–50% humidity) and (iii) freezer (?18°C). There was a significant impact of the tested harvesting methods on seed separation, thousand seed weight and purity, but not on the germination capacity. Different storage conditions and storage length significantly influenced the germination capacity. There were also generally higher germination values for the seed‐stripping material than the on‐site threshing material (ca. 70 and 60%, respectively, in the first year). Germination capacity decreased significantly with time and was <15% after 3 years. We conclude that harvested seed material from semi‐natural grassland should preferably be stored under cool conditions and used within 2 years.     

Utilization of semi‐natural grassland through integrated generation of solid fuel and biogas from biomass. II. Effects of hydrothermal conditioning and mechanical dehydration on anaerobic digestion of press fluids

A procedure (Integrated Generation of Solid Fuel and Biogas from Biomass, IFBB) was developed which uses a screw press to separate the readily digestible constituents of mature grassland biomass into a press fluid for conversion into biogas and a fibrous press cake for processing into a solid fuel. Effects of mechanical dehydration and prior hydrothermal conditioning at different temperatures (5, 60 and 80°C) on concentrations of organic compounds in the press fluid and on methane production in batch experiments were evaluated for five semi‐natural grasslands typical of mountain areas of Germany. Results show that the crude protein concentration of the press fluids was higher and crude fibre concentration was lower than that of the parent material (herbage conserved as silage). Digestion tests in batch fermenters showed that the methane yield of the press fluids was double [397–426 normal litre (NL) kg^?1 volatile solids (VS) after 13 d] that of the whole‐crop grassland silage (218 NL kg^?1 VS after 27 d) but no consistent effect of higher temperature during conditioning was observed. Within 13 d of fermentation the decomposition of the organic matter (OM) that occurred in the press fluids was 0·90, whereas after 27 d of fermentation more than 0·40 of the OM remained undigested in the whole‐crop silage, pointing at a marked reduction in retention time for anaerobic digestion of press fluids in continuous systems. Press fluids produced 0·90 of the maximum methane yield after 4 to 7 d compared with 19 days for the whole‐crop silage.     

Biomass from landscape management of grassland used for biogas production: effects of harvest date and silage additives on feedstock quality and methane yield

Biogas production from grassland biomass harvested during landscape management may help to maintain species‐rich grassland biotopes, but extensive management and late harvests often result in low‐quality biomass. Biogas production from the vegetation of Alopecuretum pratensis, Molinietum caeruleae and Caricetum gracilis, three typical grassland biotopes in north German nature reserves, was investigated in relation to harvest date. In addition, the A. pratensis vegetation was investigated for ensiling and the application of bacterial silage additives. Results indicate that biogas production might be a reasonable utilization pathway for grassland biomass from landscape management if the first cut occurs up to late summer. Methane yields of grassland biomass decreased substantially with later harvest, from up to 309 l_N kg^?1 organic dry matter (ODM) in May to below 60 l_N kg^?1 ODM in February, in correlation with increasing crude fibre contents. Caricetum gracilis vegetation was the least suitable feedstock for biogas production. It showed a rapid decline in methane yields with later harvest and 25% lower methane yields compared with other types of grassland vegetation. Application of silage additives is recommended for adequate preservation of grassland biomass from landscape management by ensiling. Addition of homofermentative lactic acid bacteria improved acidification during ensiling if sufficient fermentable sugar was available. The use of inoculant and molasses enhanced methane yields by 3–55%. Additional carbohydrate source is necessary to ensure proper ensilage when grasses are harvested after late autumn.     

Seasonal dynamics of bioenergy characteristics in grassland functional groups

Semi‐natural grasslands (SNG) are considered as bioenergy resources, either for combustion or for biogas production. To provide information on the seasonal (June–August) dynamics of herbage quantity and chemical composition, we studied the effects of factors on the proportions of four plant functional groups, chemical composition and total biomass yield at twelve sites representing three Estonian SNG types. Biomass yield increased only in alluvial meadows with the largest contribution of sedges/rushes (39%). Grasses dominated in dry‐to‐mesic meadows (62%) and other forbs in wooded meadows (55%). Concentration of fibre was highest in grasses and sedges/rushes (682 and 645 g NDF kg^?1), and lignin was highest in legumes and other forbs (103 and 113 g kg^?1). Legumes contained more C and N (447 and 25 g kg^?1) and grasses more Cl (1 g kg^?1). The highest concentrations of Mg, K and ash were in other forbs (4, 18 and 80 g kg^?1), and Ca in legumes (16 g kg^?1). The results are discussed in the context of suitability of different functional groups and SNG types for bioenergy conversion. Grasses and sedge‐/rush‐rich biomass are considered suitable for methane production. Biomass harvesting in July and minimizing the problems with N and Cl during combustion need to be considered. Forb‐rich biomass should be pre‐treated before direct combustion.     

Utilization of semi‐natural grassland through integrated generation of solid fuel and biogas from biomass. III. Effects of hydrothermal conditioning and mechanical dehydration on solid fuel properties and on energy and greenhouse gas balances

The integrated generation of solid fuel and biogas from biomass (IFBB) procedure separates biomass into a readily digestible press fluid, from which biogas is produced, and a fibrous press cake that is used as solid fuel. The effects of mechanical dehydration and prior hydrothermal conditioning (5, 60 and 80°C) on biomass from five species‐rich, semi‐natural grasslands, typical of mountain areas of Germany were investigated. Proportional reduction of ash constituents in the press cake compared with the parent material was up to 0·80, 0·61 and 0·81 for potassium, magnesium and chloride, respectively, at 60°C, resulting in potassium, magnesium and chloride concentrations in the press cake of 2·43, 1·22 and 0·93 g kg^?1 dry matter (DM). Emission‐relevant constituents were reduced by up to 0·19 (nitrogen) and 0·39 (sulphur), yielding nitrogen and sulphur concentrations of 11·13 and 0·97 g kg^?1 DM respectively. Ash softening temperatures were significantly increased up to 1250°C, falling within the range of wood fuels. Thus, quality of IFBB fuels is superior compared with conventional hay and is comparable to hay of delayed harvest in winter or the next spring. Calculated energy conversion efficiency for IFBB was up to 0·51, compared with a maximum of 0·22 for anaerobic whole crop digestion (WCD) and 0·74 for combustion of hay (CH). High energy demands in IFBB resulted in a greenhouse gas mitigation potential of up to ?4·40 t CO₂eq ha^?1 which is lower than for CH (up to ?6·17 t CO₂eq ha^?1), but higher than for WCD, which mitigated up to ?2·24 t CO₂eq ha^?1.     

乙醇水剂法提取武夷水仙茶叶籽油及其品质分析

以武夷水仙茶叶籽为原料,采用乙醇水剂法提取武夷水仙茶叶籽油,通过单因素试验考察了提取温度、料液比、乙醇浓度和pH对提取率的影响,并采用正交试验设计优化了提取工艺条件.结果显示,武夷水仙茶叶籽油最佳提取条件为乙醇浓度30％(V/V)、料液比1:7、pH 9、提取温度60℃,在该条件下武夷水仙茶叶籽油提取率为93.61％....