Contents lists available at ScienceDirect Algal Research journal homepage: www.elsevier.com/locate/algal Prospects of using biomass of N 2 -fixing cyanobacteria as an organic fertilizer and soil conditioner Mauro Do Nascimento, Marina E. Battaglia, Lara Sanchez Rizza, Rafael Ambrosio, Andres Arruebarrena Di Palma 1 , Leonardo Curatti ⁎ Instituto de Investigaciones en Biodiversidad y Biotecnología (INBIOTEC-CONICET), Mar del Plata, Argentina Fundación para Investigaciones Biológicas Aplicadas, Argentina ARTICLE INFO Keywords: Vinasse Biological N 2 -fixation Organic fertilizer Drought Soil conditioner ABSTRACT Increasing production of N-fertilizers is mandatory to support the expected demand of food over the next dec- ades. While reduced access to N-fertilizers compromises food security in some regions of the world, incorrect management in other regions causes detrimental effects on the environment. Biological N 2 -fixation is a natural process for N-fertilization of plants in natural environments which could only be partially exploited in intensive agriculture. This is mainly because the current technology of crop inoculation with live microorganisms is often constrained by the inoculant's survival and propagation in the agricultural environment. In this study, we pursued a controlled eutrophication approach to recycling nutrients from agro-industrial runoffs for the production of an organic fertilizer and soil conditioner. Biomass of a N 2 -fixing cyanobacterium was obtained using a P-enriched fermentation vinasse as a sole source of macronutrients. The cyanobacterial biomass substituted for urea in wheat growth in artificial semi-arid soil, especially when sporadic watered si- mulating a semi-arid rainfall regime. Comparative analyses suggested a higher persistence of the organic fer- tilizer in the soil than an equivalent amount of urea. This study advocates the convenience of concentrating nutrients from industrial wastewater into biomass of N 2 -fixing cyanobacteria for their re-use in crop fertilization. It discusses the advantages of separating biological fertilizer production from crop cultivation in order to circumvent the odds of the microorganisms' acclimation to the agronomic conditions, and the techno-economic challenges towards maturation of the proposed technology. 1. Introduction Agriculture plays a critical role in achieving one of the major sus- tainability goals by 2050. By then, global food production should in- crease between 60 and 110% [1]. However, this increase will be a major challenge given that agriculture is the world's single largest driver of global environmental change [2] and, at the same time, is significantly affected by these changes [3]. High agricultural productivity depends most critically on fresh water and soil fertility. Technological advances in irrigation and ferti- lization have been used quite successfully to overcome such limitations. Irrigation in agriculture consumes about 85% of the total fresh water used by humankind worldwide. This consumption yields about 45% of the global agricultural production from only 18% of the world's culti- vated area, which is operated under irrigation [4]. Higher crop yields are largely dependent on fertilization, especially N-fertilization. Water and N demand by plants are closely related. Water promotes N demand during the process of plant growth and N availability from the soil into the plant root system, regardless of the overall N content of the soil. On the other hand, N-promoted leaf expansion increases water demand by plants [4]. Nitrogen fertilizer is obtained by the industrial Haber–Bosch process from atmospheric N 2 in an energy-intensive process. It has been esti- mated that during the last decade, over 80% of the N found in proteins in the average human body was obtained through the Haber–Bosch process [5]. Demand and cost for N fertilizers are expected to continue to increase during future decades [6]. As a result, crop productivity has been limited in some regions of the world (e.g. sub-Saharan Africa) due to insufficient N fertilization. [7]. Strikingly, most of the N-fertilizer is lost to the environment in more developed or rapidly developing https://doi.org/10.1016/j.algal.2019.101652 Received 18 February 2019; Received in revised form 4 August 2019; Accepted 2 September 2019 ⁎ Corresponding author at: Instituto de Investigaciones en Biodiversidad y Biotecnología (INBIOTEC), Vieytes 3103, Mar del Plata 7600, Argentina. E-mail address: lcuratti@inbiotec.conicet.gov.ar (L. Curatti). 1 Current address, Instituto de Investigaciones Biológicas, CONICET, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Mar del Plata, CC. 1245, 7600 Mar del Plata, Argentina. Algal Research 43 (2019) 101652 2211-9264/ © 2019 Elsevier B.V. All rights reserved. T