Nanotechnology is where computer science and chemistry combine down at the atomic and molecular level to create active ingredients with particle sizes so small that they take on new and, seemingly, magical properties.

By 'small' we are talking about one millionth of a millimetre (one nanometre) – that is small enough for particles to be not much larger than an individual atom.

To put that size in context, a virus is around 100 nanometers (nm) and a blood cell is 7,000nm.

Agrochemical companies are already manufacturing crop protection products containing particles of active ingredient that are at or near the nanoscale definition of 1.0nm-100nm. At this size they are between 2,000 and 50,000 times smaller than particles in conventional agrochemicals.

A nanotechnology insecticide, for example, will contain many trillions of particles of active ingredient per litre. The massive extra surface area created by the reduction in particle size can boost potency, accelerate uptake by the plant or pest, increase solubility in the spray tank and reduce or even eliminate the risk of settlement.

Alternatively, it is possible that the performance of an agrochemical containing particles of a conventional size can be boosted simply by adding a catalyst containing nano-scale particles.

The potential of nanotechnology to create products with weird and wonderful properties is prompting the world’s largest chemical companies such as Syngenta, BASF, Bayer and Du Pont to speed up its commercial development.

Many major governments are lending their support. The 2009 budget of the US National Nanotechnology Initiative is $1.5billion. The UK’s investment is £90m over six years.

The food industry innovations are ahead of those for agriculture; some are already in the marketplace, their development fuelled by the growing demand for safe and healthy food.

So-called ‘Smart Packaging’ innovations include food containers with built-in warning strips of nano-sensors that are sensitive to the gases given off as food gets staler. The strip changes colour to indicate whether the food is fresh or not.

There is a harmless nano-spray based on protein molecules that have been manipulated to glow when in contact with harmful bacteria. Applied to fresh produce at the packing stage it can give an early warning of contamination by salmonella and E. coli.

Bayer already manufactures a plastic film ‘enriched’ with hundreds of millions of silicate particles per square metre that, although slightly above the nanometer scale, are small enough to dramatically increase the fresh life of food, especially meat, by minimising the entry into the package of the oxygen that causes discolouration.

At the same time it slows the drying out process by reducing the loss of moisture from the inside of the pack.

Up to now the brewing industry has been unable to move to plastic bottles because beer reacts with plastic. But now plastic bottles incorporating near nano-sized particles of clay that prevent the reaction between product and package for up to six months are being produced.

The two most exciting nanotechnology innovations in agriculture will be in the areas of a) early warning sensing devices for weather and diseases, and b) improved delivery systems for agrochemical inputs.

In one arable sensing scenario the cropping land of the near future will be laced with tiny granules containing minute wireless nano-sensors that can monitor in-field variations in the environment such as temperature, soil water stress and even plant stress caused by pests or disease.

At the same time, a scattering of minute bio-sensors will chemically detect the presence of disease spores long before there are visible signs of infection on the crop.

These so-called ‘smart fields’ will provide real time information on a range of soil, crop and microclimate conditions that can be located down to the nearest square metre by GPS and will be continuously transmitted to the computer in the farm office to provide a complete plant health monitoring system.

As a result, the human judgement and subjectiveness that has been the basis of crop protection assessments up to now will be strengthened by earlier and more accurate data.

Decisions on the timing of applications of inputs will be improved so that the effectiveness of irrigation and fertiliser and agrochemicals can be maximised

Additionally, these minute in-field sensors will provide all the information needed to programme sprayers to operate a variable spraying rate across the field to match in-field variations in, say, disease, that are unseen by the human eye.

The small nano-particles at the heart of this monitoring innovation are likely to be created by what is called a ‘bottom up’ process, that is their manufacture starts with the smallest units (atoms or molecules) which are micro-modified to take on new properties.

These tiny new units are then added to suitable carriers such as granules or solutions for application in the field.

In contrast, most of the improved crop input delivery systems are being developed using the ‘top down’ process, in which particles of conventional substances are reduced to a minute fraction of their normal size, certainly to less than 500nm and often down to true nanotechnology sizes of less than 100nm.

At this minute scale, they take on radically different properties without resorting to the molecular tinkering of the ‘bottom up’ approach.

The chemical and physical performance of the active ingredient is increased – the product, usually in the form of a dispersion of nano-particles, becomes more potent and gets absorbed more rapidly by the target.

This provides an opportunity to dramatically reduce application rates of chemical per hectare (but not necessarily less spray volume per hectare) without jeopardising pest or disease control.

This has huge significance for agrochemical companies and farmers coming under increasing pressure from regulatory bodies to reduce the chemical load applied per hectare of cropped area.

Syngenta is one of the most active companies in the ‘top down’ approach. Advances in formulation technology have already reduced the active ingredient particles in some of its products down to a size approaching the nano scale.

Karate insecticide, for example, controls pests of cotton, rice and soya bean with near nano-sized particles of a pyrethroid active ingredient encased in tiny, bacteria-sized, water dispersible capsules.

Once applied, the quick-release micro-capsules adhere strongly to the foliage and immediately begin releasing the active ingredient.

A similar technique patented by Syngenta is applied to another insecticide, but in this case the micro-capsules will only release the active ingredient if they come into contact with an alkaline substrate similar to an insect’s stomach – thus improving targeting and reducing unnecessary escape of chemical into the environment.

But despite its major benefits, nanotechnology has a rocky road ahead. Concerns are being expressed about the wider implications of the technique by eminent scientists, government safety authorities and environmental watchdogs such as Friends of the Earth.

Their concerns relate mainly to the fate of manipulated molecules and minute particles of pesticides when released into the environment.

Are the particles so small that they can enter human cells and pose a health hazard? Will the enhanced solubility and mobility of tiny pesticide particles pose a spectacular run-off pollution problem?

Agrochemical companies involved in developing nanotechnology are desperate to avoid a backlash. Most are back-pedalling on earlier enthusiastic claims of an agricultural revolution in the offing and are playing down the extent of their involvement in the technology, but remain convinced of the potential benefits.

The debate is just warming up, but it has such huge implications that it could soon eclipse the GM crops issue.

source...
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