Commercial energy crops are typically densely planted, high-yielding crop species which are processed to bio-fuel and burnt to generate power. Woody crops such as willow or poplar are widely utilised, as well as temperate grasses such as Miscanthus and Pennisetum purpureum (both known as elephant grass). If carbohydrate content is desired for the production of biogas, whole-crops such as maize, Sudan grass, millet, white sweet clover, and many others can be made into silage and then converted into biogas.
Through genetic modification and application of biotechnology plants can be manipulated to create greater yields, high energy yields can also be realized with existing cultivars.. However, some additional advantages such as reduced associated costs (i.e. costs during the manufacturing process) and less water use can only be accomplished by using Genetically_modified_crops#Biofuel genetically modified crops.
Definition and demarcation
Energy crops are agricultural crops grown with the main objective of producing energy as distinct from plants for food production, forage crops and industrial crops. Wild plants, the z. B. are used as fuel wood energetically, are not counted among energy crops. Forest plants grown on agricultural land for energy use (for example in short rotation plantations) are usually included. In part, energy plants are only spoken when energy is used throughout the plant.
Decisive is the use of the plant. So corn both as sweet corn for human consumption as well as feed maize (corn silage) for animal feed or as energy maize are cultivated for biogas production. Depending on the direction of use, the varieties and cultivation methods used for energy crops differ in part from those used for food and feed.
Plant groups and usage
Numerous plant species are suitable for energetic use. Among them are both traditional crops of agriculture, for the partially optimized for the use of energy varieties are cultivated (eg rapeseed, corn), as well as crops that have not been used or barely arable, but from the aspect of energy use are interesting (for example, Miscanthus, Perennial Silphie, Sida hermaphrodita). So far, cultivation has concentrated on already widespread arable crops. The breeding of new varieties and the use of new crops are just beginning. The table below lists some plant species and groups cultivated in Central Europe as energy crops. Energy crops with significant acreage or potential in other regions may be affected. a. Soy, oil palm, purging nut and sugar cane.
Increasingly, fast-growing woody plants such as willows, poplars and robinia are being cultivated on agricultural sites in Central Europe in order to meet the growing demand for woody biomass. This shows that especially moist field locations are suitable for growing willows and poplars, as their growth is strongly linked to water availability. For example, potential estimates for Germany show special favorable locations in the northwest (methods and results, with data and maps in the sources). When growing, however, it should be noted that the high water consumption of plants can also have a negative impact on vulnerable aquatic ecosystems. Nevertheless, the cultivation offers an alternative form of use for crowded farmland.
Energy crops in Central Europe and their use
| raw material | method | product | Plant (fruit) |
|---|---|---|---|
| sugar and starchy plant parts | Fermentation ( ethanol fermentation ) | biogenic liquid fuel ( bioethanol , fuel additives ) | Sugar beet , potato , corn grain , corn grain |
| oily plant parts | Pressing / extracting, (transesterification) | biogenic liquid fuel ( vegetable oil fuel , biodiesel ) | Rapeseed , sunflower seeds |
| biogenic solid fuels (whole or partial plant, piece wood , wood chips , pellets ) | combustion | Heat and electricity from biogenic solid fuel | Trees , grasses , cereals (grain), miscanthus |
| fermentable biomass ( substrate : whole or partial plant, organic waste) | Fermentation (anaerobic degradation with methane formation ) | Heat and electricity from biomass, biogenic fuel gas ( biomethane ) | Corn, grains, cereals, sugar beet |
Energy crops are used for the production of heat and electrical energy as well as biofuels. A variety of use paths are used, especially fermentation or biogas production in biogas plants (use as fermentation substrate), combustion (use as biofuel) and various other forms of complete or partial conversion of the biomass (including pyrolysis, production of synthetic biofuels (BtL)). Energy carriers are either the plant substrate itself after comminution (eg biogenic solid fuels such as firewood,Pellets), pressing / extraction or further processing (eg biogenic liquid fuels such as vegetable oil fuel, bioethanol, biodiesel, BTL) or energy-rich gases obtained by gasification of the biomass (eg biogenic fuel gases such as biogas, syngas, hydrogen).
Types
By state
Solid biomass
Energy generated by burning plants grown for the purpose, often after the dry matter is pelletized. Energy crops are used for firing power plants, either alone or co-fired with other fuels. Alternatively they may be used for heat or combined heat and power (CHP) production.
To cover the increasing requirements of woody biomass, short rotation coppice (SRC) were applied to agricultural sites. Within this cropping systems fast growing tree species like willows and poplars are planted in growing cycles of three to five years. The cultivation of this cultures is dependent on wet soil conditions and could be an alternative for moist field sieds. However, an influence on local water conditions could not be excluded. This indicates that an establishment should exclude the vicinity to vulnerable wetland ecosystems.
Gas biomass (methane)
Anaerobic digesters or biogas plants can be directly supplemented with energy crops once they have been ensiled into silage. The fastest growing sector of German biofarming has been in the area of "Renewable Energy Crops" on nearly 500,000 ha (1,200,000 acres) of land (2006). Energy crops can also be grown to boost gas yields where feedstocks have a low energy content, such as manures and spoiled grain. It is estimated that the energy yield presently of bioenergy crops converted via silage to methane is about 2 GWh/km2 (1.8×1010 BTU/sq mi). Small mixed cropping enterprises with animals can use a portion of their acreage to grow and convert energy crops and sustain the entire farms energy requirements with about one fifth of the acreage. In Europe and especially Germany, however, this rapid growth has occurred only with substantial government support, as in the German bonus system for renewable energy. Similar developments of integrating crop farming and bioenergy production via silage-methane have been almost entirely overlooked in N. America, where political and structural issues and a huge continued push to centralize energy production has overshadowed positive developments.
Liquid biomass
Biodiesel
European production of biodiesel from energy crops has grown steadily in the last decade, principally focused on rapeseed used for oil and energy. Production of oil/biodiesel from rape covers more than 12,000 km² in Germany alone, and has doubled in the past 15 years. Typical yield of oil as pure biodiesel may be is 100,000 L/km2 (68,000 US gal/sq mi; 57,000 imp gal/sq mi) or more, making biodiesel crops economically attractive, provided sustainable crop rotations exist that are nutrient-balanced and preventative of the spread of disease such as clubroot. Biodiesel yield of soybeans is significantly lower than that of rape.
Typical oil extractable by weight
| Crop | Oil % |
|---|---|
| copra | 62 |
| castor seed | 50 |
| sesame | 50 |
| groundnut kernel | 42 |
| jatropha | 40 |
| rapeseed | 37 |
| palm kernel | 36 |
| mustard seed | 35 |
| sunflower | 32 |
| palm fruit | 20 |
| soybean | 14 |
| cotton seed | 13 |
Bioethanol
Energy crops for biobutanol are grasses. Two leading non-food crops for the production of cellulosic bioethanol are switchgrass and giant miscanthus. There has been a preoccupation with cellulosic bioethanol in America as the agricultural structure supporting biomethane is absent in many regions, with no credits or bonus system in place. Consequently, a lot of private money and investor hopes are being pinned on marketable and patentable innovations in enzyme hydrolysis and the like.
Bioethanol also refers to the technology of using principally corn (maize seed) to make ethanol directly through fermentation, a process that under certain field and process conditions can consume as much energy as is the energy value of the ethanol it produces, therefore being non-sustainable. New developments in converting grain stillage (referred to as distillers grain stillage or DGS) into biogas energy looks promising as a means to improve the poor energy ratio of this type of bioethanol process.
By dedication
Dedicated energy crops are non-food energy crops as giant miscanthus, switchgrass, jatropha, fungi, and algae. Dedicated energy crops are promising cellulose sources that can be sustainably produced in many regions of the United States.
Additionally, the green waste byproducts of food and non-food energy crops can be used to produce various biofuels.
Cultivation extent and development
In Germany energy crops are grown on 2.28 million hectares (as of 2011). This corresponds to 19% of the total arable land in Germany. Of these, more than one million hectares are devoted to the cultivation of rapeseed for biodiesel and vegetable oil fuel, plants produce more than 500,000 hectares for biogas production, and over 250,000 hectares are used to grow sugar and starch plants for bioethanol. The cultivation of energy crops has increased dramatically in recent years - in 1998 the total area under cultivation for renewable resources in total (including cultivation for material use) was less than 500,000 ha. According to current estimates, the Agency for Renewable Resources (FNR) estimates the acreage for renewable raw materials in Germany in 2012 at around 2.5 million hectares. The majority of these, 2.1 million hectares, are grown using energy crops. The most important energy crops are still rapeseed for biofuels as well as corn, other cereals and grasses for biogas plants. The smaller part of the acreage is used for renewable raw materials, which are used for chemical-technical purposes in the industry.
Promotion
The cultivation of energy crops has so far been financially supported under the Common Agricultural Policy of the European Union with direct payments (so-called energy crop premium). This promotion of a maximum of € 45 / ha was abolished in 2010. Under the compulsory set-aside until 2007, farmers were not allowed to grow food or feed on part of their arable land and were granted a set-aside premium. However, energy crop cultivation on these areas was permitted. An energy crop premium is only granted to farmers for non-decommissioned land. By abolishing compulsory set-aside and the energy crop premium, the direct promotion of energy crop cultivation is losing importance.
Environmental effects
By using energy crops, energy sources can be provided in an environmentally sound manner. The reduction of carbon dioxide emissions (CO2) to reduce the greenhouse effect is an important factor. The climate impact of the cultivation and use of energy crops is being discussed controversially. In addition to the CO2 savings through the use of renewable raw materials, climate balance sheets of arable farming also need to calculate the climate-relevant emissions of nitrous oxide N2O, which arises especially in nitrogen-fertilized arable crops. Cultivation and land use can also have a major impact on the climate impact of energy crops: clearing rainforests, cultivating peatlands or changing grassland to produce energy crops releases large quantities of greenhouse gases.
The European Union has adopted the Renewable Energy Directive (EC), which will apply from June 2009. Amongst other things, it sets sustainability criteria for the promotion of biofuels and their inclusion in EU biofuels targets. These sustainability criteria were transposed into German law with the Biomass Electricity Sustainability Ordinance (Biost-NachV, valid from August 2009) and the Biofuel Sustainability Ordinance (Biokraft-NachV, valid from September 2009).
One goal of energy crop research is to improve the energy yield per acreage by using whole plants and optimizing processes. In addition, methods for expanding the usable area are being investigated, eg. Breeding of saltwater algae in desert areas or cultivation of the frugal oil plant Jatropha.
However, the areas needed for growing energy crops could also be used for other economically and ecologically sensible purposes (eg renewable raw materials for material use, extensification of agriculture). In addition, they are no longer available for food production (area competition). In view of population growth, ethical issues are discussed in this context, in particular the use of foodstuffs such as cereals (eg grain burning) is criticized (competition for use).
The cultivation of energy crops is often operated as agriculture with high intensity, u. a. with regard to fertilizer and pesticide use, which can lead to ecological damage. The cultivation of plants from foreign regions of origin as energy crops carries risks, eg. by the spread of neophytes.
Source from Wikipedia
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