THEOFANIS .A. GEMTOS, SPYROS FOUNTAS, CHRISTOS CAVALARIS

LABORATORY OF FARM MECHANISATION, DEPARTMENT OF AGRICULTURE, CROP PRODUCTION AND RURAL ENVIRONMENT, UNIVERSITY OF THESSALY, GREECE

Environment and Second Generation Biofuels

Introduction

Second generation biofuels (i.e bioethanol), but also biomass use for burning, are expected to use crop residues and whole crops.

The removal of all biomass can have several adverse effects to the soil and the ecosystem.

DIRECTIVE 2009/28/EC OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL of 23 April 2009, Article 18 par. 3 requires that:

Any relevant information on measures taken for soil, water and air protection, the restoration of degraded land, the avoidance of excessive water consumption in areas where water is scarce to be declared for the biofuels produced

Objectives

The aim of the present paper is to make an account of the problems that whole plant use for second generation biofuels can cause to the soil and possible methods to alleviate them and secure the sustainability of the raw material production system.

In this paper the effects to the soil fertility will be presented.

Risks of soil degradation

A study funded by the European Commission on European soils revealed that six factors can be major threats (SOCO team):

1. Soil erosion by water and wind2.Soil organic matter reduction3. Soil biodiversity4. Soil compaction5. Soil pollution by heavy metals6. Soil acidification

The first four factors will be affected by whole crop removal.

What second generation biofuels whole biomass use will cause

It will cause:1.The soil to remain bare for periods of the

year enhancing erosion2.The removal of all organic matter leading to

reduction of soil organic matter3.Soil compaction by the movement of heavy

harvesting and transportation machinery4.Reduce biodiversity

Soil erosion

Is defined as the removal of soil particles from higher to lower parts of the land through the action of water runoff or the wind.

The phenomenon is considered to start from the rain or irrigation water drops impact on bare soil.

This impact brakes the soil aggregates, producing small soil particles that are closing soil surface pores reducing water infiltration and are easily moved by water or wind

Soil organic matter

Is a basic factor of soil fertility as it binds the soil mineral aggregates increasing their stability, improves water holding and cation exchange capacity, when decay provides N to the plants, it contributes to better soil structure.

It is produced by the organic part of the plants.Most stable organic matter is produced by the

high lignin content of the roots, while the cellulosic material of the aerial part is easily decomposed.

Recent research proved that without the cellulosic material of the aerial part the root biomass cannot be decomposed by the soil microorganisms.

Therefore the whole biomass removal can affect also root biomass decomposition

Soil biodiversity

Huge amounts of microorganisms and upper animals are living in the soil. They are the living soil.

They are using biomass for their energy needs.

Removal of the biomass will reduce their feedstock and cause reduction of their numbers and activities.

Their activities in the soil are very important for soil fertility.

But also for soil structure. Especially worms can improve soil structure.

Soil Compaction

It is a destruction of soil structure due to the excess loads imposed by heavy machinery.

It causes reduction of soil porosity (reduced water infiltration, reduced drainage, reduced water holding capacity), increases the energy consumption for soil tillage, causes difficulties in plant emergence.

Biomass harvesting and heavy transportation vehicles, especially under wet soil conditions cause compaction.

How we can alleviate the problems

At the moment research suggests that we should act in four directions:

1.Introduce crop rotations and keep the soil covered all the year round with minimum periods where the soil remains bare

2.Use cover crops as green manure by leaving them on/or in the soil

3.Use reduced or no tillage4.Use controlled traffic or new mechanisation

systems with small size, light machinery.

Crop rotation

It is defined as the succession of crops in a cropping system.

Properly designed it can have crops following each other minimising the periods of bare soil.

The crops can be removed (totally or partially)Some crops can be used as cover crops and as

green manure to secure the requirements for cellulosic material to assist root decay and keep the soil covered for longer periods.

Combination of shallow and deep root plants can enhance soil exploitation

Perennial energy crops can offer the continuous soil cover, a good root system and reduced costs as the establishment cost will be spread in more than one year.

Cover crops

Any crop used to keep the soil covered by vegetation that can be incorporated in the soil is called cover crops

They are left on the soil for protection from erosion, they increase surface soil organic matter and aggregate stability and improve biodiversity.

They facilitate the root biomass decay

Reduced or no tillage

Conventional tillage uses plough for soil loosening . This inverts the soil surface layer burying all crop residues and leaving soil surface bare.

Conservation tillage is defined as the system that leaves at least 30% of the soil surface covered by crop residues

It can include a shallow tillage without soil inversion or no tillage

Reduced and mostly no till offer several advantages for the soil fertility and the sustainability of the agricultural systems.

Using the tool for estimation of soil C stocks associated with management changes of croplands based on IPCC default data developed by Joint Research Centre of the European Commission, Institute for Environment and Sustainability (http://www.jrc.ec.europa.eu/) we had the following results:

For warm temperate dry zone of Greece (Eastern part), for high activity clay soils, long term cultivated transition from full tillage to No-till both with high inputs without manure the C stock changed from 33.3 Mg C/ha to 36.7 Mg C/ha. Change to reduced tillage the stock was 34.3 Mg C/ha.

The respective figures for warm temperate moist area (west of Greece) the respective changes were from 69.4 Mg C/ha to 80.4 Mg C/ha for No till and 75.6 for reduced tillage.

For Sandy soil the C stock with full tillage was estimated at 26.8 Mg C/ha and changed to 31.1 with no tillage and high inputs without manure.

Principles of conservation agriculture

According to ECAF, CA offers

provides similar or even higher yields through improvements in soil structure, organic matter and overall soil fertility;

lowering production costs through reduced inputs of energy, labour and machinery in the short and long term, and fertilizers, water and pesticides in the medium and long term, thus raising related productivity and efficiency

mitigating CO2 emissions through reduced fuel consumption and sequestration of atmospheric carbon into soil organic matter, and reducing N2O and NH4 emissions through reduced use of mineral nitrogen and improved soil drainage;

reducing runoff and erosion through better soil aggregate stability and improved water infiltration, and protective cover of the soil by crops and/or crop residues;

diminishing off-site damage of infra-structures and pollution of water bodies through less runoff with a much reduced sediment load;

maintaining in-field and off-site biodiversity through the absence of destructive soil disturbance, protective soil shelter and less off-site transport of contaminants;

maintaining the diversity of rural landscape through enhanced crop and species diversity and cover crops;

maintaining less favoured rural areas under production through adoption of economically and environmentally viable production methods.

Reducing compaction problems

Controlled traffic: Is proposed to reduce the problem by using machinery with wheels spacing at 3 m, all machinery working width multiples of 3 m.

Soil lanes at 3 m width will be used for the traffic.

This is feasible using the new RTK- GPS technology offering accuracy of 20 mm and the new guidance systems on tractors and machinery

Controlled traffic

Small size mechanisation system

The aim to reduce machinery operators costs leads to increases in the size of farm machinery.

Harvesting machinery of more than 20 t weight are used.

Soil compaction can affect soil layers deeper than the ploughing depth which remain for many years affecting yields.

New technology can develop autonomous tractors and machinery. In this case the operator costs are eliminated and so the need for new larger and heavier machinery.

The small size light tractors and machinery can work 24 hours per day doing the filed operations with minimum soil compaction.

A fleet of small size machinery can offer a new mechanisation system that minimises soil compaction and other filed operations to remove comaction.

Conclusions

Whole crop harvesting for second generation biofuels production can cause problems to the soil and threats the sustainability of the system.

New production systems have to be developed to reduce all negative effects. These systems have to use new crops rotations including perennial and cover crops , conservation tillage and controlled trafic.

Acknowlegments

This paper is part of the project “Friendly to the environment biomass production” funded by the GSRT of Greece.

biomass.agr.uth.gr