‘It is easier said than done, in discussions on the biobased economy, to return the minerals to the land. The question often overlooked is, whether the farmer needs them at that specific moment. That is the question we address in the BioNPK project. We discuss which minerals should be reclaimed. For agriculture should not become biobased economy’s waste pipe.’ Says Tjitse Bouwkamp, policy advisor to the Dutch agricultural association ‘Productschap Akkerbouw’.
BioNPK is a Dutch Biorefinery Cluster project, intended to develop technological concepts for minerals reclamation from agro-food industry’s waste streams. In particular nitrogen (N), potassium (K) and phosphate (P). BioNPK’s project leader is Dirk Vermeulen, program manager at Cosun Food Technology Centre. His own subject is minerals reclamation from sugar beet.
The right minerals at the right moment
‘We process waste streams from sugar production into biogas and digestate. We can separate the latter into a dry and a wet fraction. The wet fraction is best suited for N, P and K reclamation and valorisation. These minerals can be used as fertilizer in agriculture. But often, those minerals are absorbed in the dry fraction, which stands in the way of their use on the land because the farmer has to comply to many rules of minerals management.’
That is an area well known to Tjitse Bouwkamp. He is the program leader to the knowledge program Master plan Minerals Management, which aims to arrive at an emission neutral agriculture in 2030. One of the main questions in the program is, how the farmer can deliver fertilizer to the crop at the time and place, and in the quantity required, hence reducing losses to the environment as much as possible. Nitrogen, for instance, is of no use to the plant in autumn, it will largely be leached from the soil. But the plant does need it in spring, in order to grow.
Which technology is best suited for this goal, and what is economically achievable? BioNPK performs tests to find an answer to those questions. Companies involved include AVEBE (potato starch), Bioclear (biological solutions), and Bumaga (knowledge centre for paper and board).
Dirk Vermeulen: ‘Bioclear will investigate the possibility of reclaiming phosphate from the thick fraction using bacteria.’ Tjitse Bouwkamp: ‘The perfect result would be to produce separate minerals fractions and a thick ‘clean’ fraction consisting of organic matter for soil quality improvement, which does not claim environmental space for minerals. But precisely that result requires a maximum of energy, chemical agents to reclaim minerals, and investment. That would harm sustainability. There is an optimum to what can be achieved.’
Tests in the field
‘Therefore we also study alternative pathways in BioNPK. We research the production of a thick fraction of clean organic matter, and several wet fractions containing various combined concentrations of minerals, optimally suited for a particular moment in the crop cycle. The Master plan Minerals Management tests these in the field. On the basis of the outcome, the participating companies can judge whether they will have a solid business case for agriculture, or whether they could put these minerals to better use in other products.’
‘The ideal outcome? Separate streams for nitrogen, potassium and phosphate, and a ‘clean’ fraction of organic matter.’
Courtesy DBC, Dutch Biorefinery Cluster