Ecological intensification by integrating biogas production into nutrient cycling : Modeling the case of Agroecological Symbiosis
Koppelmäki, Kari ; Parviainen, Tuure ; Virkkunen, Elina ; Winquist, Erika ; Schulte, Rogier P.O. ; Helenius, Juha - \ 2019
Agricultural Systems 170 (2019). - ISSN 0308-521X - p. 39 - 48.
Biological nitrogen fixation - Localized agrifood system - Nutrient losses - Organic farming - Renewable energy - Sustainable intensification
There is growing demand to produce both food and renewable energy in a sustainable manner, while avoiding competition between food and energy production. In our study, we investigated the potential of harnessing biogas production into nutrient recycling in an integrated system of organic food production and food processing. We used the case of Agroecological Symbiosis (AES) at Palopuro, which is a combination of three farms, a biogas plant, and a bakery, as a case to explore how biogas production using feedstocks from the farms can be used to improve nutrient cycling, and to calculate how much energy could be produced from the within-system feedstocks. The current system (CS) used in organic farms, and the integrated farm and food processing AES system, were analyzed using Substance Flow analysis. In the AES, annual nitrogen (N) and phosphorus (P) surpluses were projected to be reduced from 95 kg ha−1 to 36 kg ha−1 and from 3.4 kg ha−1 to −0.5 kg ha−1 respectively, compared to the CS. Biogas produced from green manure leys as the major feedstock, produced 2809 MWh a−1. This was 70% more than the energy consumed (1650 MWh a−1) in the systemand thus the AES system turned out to be a net energy producer. Results demonstrated the potential of biogas production to enhance the transition to bioenergy, nutrient recycling, and crop productivity in renewable localized farming and food systems.
Nitrogen-induced new net primary production and carbon sequestration in global forests
Du, Enzai ; Vries, Wim de - \ 2018
Environmental Pollution 242 (2018). - ISSN 0269-7491 - p. 1476 - 1487.
Biological nitrogen fixation - Carbon sequestration - Carbon-nitrogen interactions - Net primary productivity - Nitrogen deposition
Nitrogen (N) deposition and biological N fixation (BNF) are main external N inputs into terrestrial ecosystems. However, few studies have simultaneously quantified the contribution of these two external N inputs to global NPP and consequent C sequestration. Based on literature analysis, we estimated new net primary production (NPP) due to external N inputs from BNF and N deposition and the consequent C sinks in global boreal, temperate and tropical forest biomes via a stoichiometric scaling approach. Nitrogen-induced new NPP is estimated to be 3.48 Pg C yr−1 in global established forests and contributes to a C sink of 1.83 Pg C yr−1. More specifically, the aboveground and belowground new NPP are estimated to be 2.36 and 1.12 Pg C yr−1, while the external N-induced C sinks in wood and soil are estimated to be 1.51 and 0.32 Pg C yr−1, respectively. BNF contributes to a major proportion of N-induced new NPP (3.07 Pg C yr−1) in global forest, and accounts for a C sink of 1.58 Pg C yr−1. Compared with BNF, N deposition only makes a minor contribution to new NPP (0.41 Pg C yr−1) and C sinks (0.25 Pg C yr−1) in global forests. At the biome scale, rates of N-induced new NPP and C sink show an increase from boreal forest towards tropical forest, as mainly driven by an increase of BNF. In contrast, N deposition leads to a larger C sink in temperate forest (0.11 Pg C yr−1) than boreal (0.06 Pg C yr−1) and tropical forest (0.08 Pg C yr−1). Our estimate of total C sink due to N-induced new NPP approximately matches an independent assessment of total C sink in global established forests, suggesting that external N inputs by BNF and atmospheric deposition are key drivers of C sinks in global forests. Based on a stoichiometric scaling approach, we estimated that nitrogen-induced new net primary production is a key driver of C sinks in global forests.