Protein Crop Options And Climate Change

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A conservative estimate shows that direct human consumption of plant protein, rather than indirect (via meat), has the potential to reduce the claim on natural resources such as land and fossil fuels 4-6 fold (Smil, 2000; Pimentel and Pimentel, 2003). It should be realised, however, that the meat chain has been optimised for thousands of years, resulting in efficient use of almost the whole animal (meat as well as skin, hairs, bones, gut, etc.). When replacing meat with NPFs, by analogy, all parts of the protein crop should be put to use, in order to remain competitive with respect to sustainability. Consequently, it is of the utmost importance to consider what options exist for the non-protein fraction of the raw material. Any crop that is used to produce protein-rich food products will also produce residues that cannot be used for the NPFs, for seed protein content is just 20-40%. These residues may arise in various different forms and may have different compositions depending on the crop used, the part of the production process where they arise, and the actual production techniques used. This means that both the environmental impact and the economic value of the non-protein fraction can vary greatly.

To study the non-protein fraction, information is needed on the constituents of any crop that could potentially be used for its protein. Of the main commercial food crops the main constituents other than protein are carbohydrates (starch and - to a lesser extent - sugars) and oil or fat. If we widen the scope to more unusual sources of plant protein there may be a need to include a cellulose/lignin fraction. In Europe, crop options might include lupin, pea, quinoa, triticale, lucerne, grasses, rapeseed/canola and potato (Linnemann and Dijkstra, 2002). Outside Europe, at least soy should be added.

For each constituent of the non-protein fraction there are different options. Firstly, for commercial food crops (such as pea or soy) the options are likely to be food, feed, industrial raw materials and energy production, whereas for the crops that are high in cellulose/lignin (such as grass) the options will be feed (cellulose only), industrial raw materials and energy production (Table 10.2). For all of these options estimations must be made with regard to their economic value, in order to be able to judge how realistic any given option is. Furthermore, economic value is also important when it comes to attributing environmental impacts to the different fractions of a given crop.

Table 10.2 Possible uses of the non-protein fractions

Food

Feed

Raw materials

Energy

Carbohydrates

+

+

?/+

?/+

Oil/fat

+

+

+

+

Cellulose/lignin

-

+/-

?/+

+

A possible tool for assessing uses that are available for the non-protein fractions would be a kind of scorecard. An example for such a scorecard is given in Table 10.3 for an imaginary crop X, with 25% protein, 25% carbohydrates, 25% oil/fat and 25% cellulose/lignin. Please note that, although the scorecard is given here as a 2-dimensional table, a multidimensional, spreadsheet-based card is envisaged, allowing for easy calculation of economic values and environmental impacts.

Table 10.3 Non-protein scorecard for imaginary crop X

Food

Feed

Stock

Energy

Carbo

Main use 1:

syrup

pig feed

syngas

biocrude

hydrates

replaces:

corn syrup

maize

mineral oil

mineral oil

Oil/fat

Main use 1:

cooking oil

chicken feed

cleaning agent

biodiesel

replaces:

sunflower oil

maize oil

palm oil

mineral oil

Main use 2:

-

-

plasticiser

-

replaces:

-

-

mineral oil

-

Cellulose/

Main use 1:

unsuitable

unsuitable

unsuitable

co-firing

lignin

replaces:

-

-

-

coal

In every use/replace combination various aspects can be addressed. Technical aspects must be considered, possibly leading to the verdict unsuitable, if there are very high technical barriers. Likewise economic aspects need to be taken into account, since unrealistically high costs could also rule out options. From the environmental perspective, the same scheme would serve to find the best combination of environmental benefits. Each prospective use can be given an estimated environmental impact, which can then be compared to the environmental impact of the substance it replaces. The information required to use the scorecards is:

• Information on the composition of a specific crop, such as peas.

• Information on the economic attributes of the crop's production chain.

• Information on possible uses for non-protein agricultural products in general, to serve as a backbone for more crop-specific investigations.

• Information on the environmental impacts of the crop production chain.

• Information on the environmental impacts of the replaced product chain using the same methodology as the crop chain.

The contribution of this analysis to sustainability is evident. For without useful application for the non-protein fraction a protein transition is simply not feasible for environmental reasons, because the potential 4-6 fold gain mentioned above would be largely offset by the added waste (up to 80% of the crop). The future results of the project are therefore likely to primarily influence crop selection. As a preliminary result, generally, oil crops seem preferable over starchy crops with regard to biofuel production.

Combined production of plant protein and biomass was the basis for this particular analysis. Since the EU is striving for self-sufficiency in both areas they will be interested. The protein transition and the biomass transition going handin-hand towards more sustainable production of protein and energy, respectively, is a clear example of a 'win-win' situation and it illustrates that transitions rarely go alone. If, indeed, the non-protein fraction of a protein crop is utilised for sustainable energy production, no additional, dedicated crop will be required. The converse is also true: it would be a waste to burn the high-quality protein in a dedicated energy crop. Combining sustainable production of protein and energy in one crop seems ideal to combat agricultural resource depletion and pollution, as well as climate change.

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