Use of bioenergy is based on the cultivation of renewable raw materials or the use of waste materials Leftovers, Slurry or straw. For the production of gaseous and liquid bioenergy, the NawaRo's So far mainly classic annual crops such as rapeseed, maize, rye or wheat have been used. Especially when choosing energy crops, there is also an increasing search for alternatives. Current studies show that the perennial plants also offer good conditions for the energetic use of biomass. Therefore, the potential of the perennial energy crops should be examined in more detail in today's article.
Revolution in agriculture?
Humans have been practicing agriculture for around 10.000 years to secure their food base. By adopting and developing the Agriculture we were able to emancipate ourselves from the nomadic way of life as hunters and gatherers and found permanent settlements. Focused on the positive developments, we owe a great deal to agriculture.
It should not be forgotten that the most important food crops such as barley, maize, rice or wheat are all annual. As a result, farmers on all continents are used to a one-year cultivation rhythm and are increasingly fine-tuning the individual cultivation steps (seedbed preparation, sowing, fertilization, crop protection, harvesting) in order to improve yields and less with the basic cultivation system. Concentrating on perennial plants is therefore almost a small revolution. On the basis of which arguments could this reorientation still be useful?
Perennial bioenergy plants expand the range of energy plants
Botanists distinguish between perennial plants that live for at least 2 years, but only bloom once and then die (hapaxanthens), and those perennials that bloom and bear fruit year after year. The latter are also known as perennials and are increasingly in the interest of economic use. I would like to take a closer look at the perennials.
Here are some examples of perennial plants, which as Energy plant in discussion with high potential are:
- Miscanthus (Chinese reed)
- Jatropha curcas (Purgi nut)
- Sakhalin Knotweed (Igniscum)
- Streaky silphia (see article "Silphie as an energy plant")
- Napier grass (elephant grass)
- And of course all trees and shrubs are included (see article "Dendromass from short rotation plantations"), which have not yet been counted among the arable plants
Persistent plants show different peculiarities compared to the annual plants. The multiplication of the perennial plants takes place mainly in a vegetative way and is less concentrated on the sexual reproduction.
In addition, the perennial plants increasingly form bulbs and bulbs, which they use to store nutrients and thus enable wintering.
The seeds are comparatively large and support the rapid development of the cotyledons after germination. The number of seeds produced is also lower than that of annual plants, since the pressure to spread within a season is not so great for perennials.
Benefits of perennials
Below is a list of some of the benefits of perennials. As usual, exceptions confirm the rule and none of the advantages is present in every perennial plant or in any annual plant.
- Cultivation costs: less tillage (energy and cost intensive!) Necessary, since the annual sowing and soil preparation can be omitted.
- Soil and water protection: Perennial plants usually have a deep, extensive root system, which reduces the risk of soil erosion and binds dissolved nitrogen before it contaminates ground and surface water (eutrophication).
- Use of herbicides: Is very competitive with many classic "weeds" and the need to use herbicides is low.
- Stress resistance: Have adapted to periods of dormancy (cold periods, dry periods etc.) and can thus survive the winter or times of low rainfall.
- New acreage: this high flexibility in terms of environmental conditions enables the perennials to grow in problematic regions.
- Area competition: As a rule, perennials are not as nutrient-rich as the annual plants. However, since this fact is not so important for energetic use, it offers the advantage that the competitive pressure of perennials is not so high for arable land that is also suitable for high-quality food crops.
Disadvantages of perennials
Where there is light, there is usually also shade. So the perennial plants still show various disadvantages when compared to the tried and tested annual crops. Here is an overview:
- Perennial plants often show even lower yields than the annuals selected for centuries
- Appropriate harvesting and processing machines (e.g. pelleting machines) are still in the development stage
- The tying up of land for several years leads to problems for the farmer when he wants to change the crop, which increases the response time to changes in EU agricultural policy.
- A comparatively small amount of experience about the influence of the perennials on the hydrological situation at the site. In general, it can be stated that perennial plants absorb more rainwater than annual plants because of their year-round growth.
- The missing stage of fallow land every few years, combined with the absence of plowing, can improve the conditions for "pests".
- Some species also have slag burning problems when chopped.
Conclusion on alternative energy crops
The advantages and disadvantages of individual cultures should be carefully weighed before breaking new ground. In any case, perennial plants will bring a breath of fresh air into the previous cultivation systems for energy crops and give this modern branch of agriculture more flexibility and hopefully more color to the fields. Furthermore, because of their often very high cellulose content, these “next generation energy crops” are particularly good for energy products such as Next generation biofuels suitable (e.g. cellulose-ethanol).
Finally, I would like to mention another important group of innovative energy crops. However, this is not found on land or in classic agriculture, but in the water or in specially built ponds in the country. Of course there is talk of Micro and macro algae, which will also provide new forms of bioenergy generation in the future.