Oliver Bens

Hydrothermal carbonization of biomass residuals: a comparative review of the chemistry, processes and applications of wet and dry pyrolysis

The carbonization of biomass residuals to char has strong potential to become an environmentally sound conversion process for the production of a wide variety of products. In addition to its traditional use for the production of charcoal and other energy vectors, pyrolysis can produce products for environmental, catalytic, electronic and agricultural applications. As an alternative to dry pyrolysis, the wet pyrolysis process, also known as hydrothermal carbonization, opens up the field of potential feedstocks for char production to a range of nontraditional renewable and plentiful wet agricultural residues and municipal wastes. Its chemistry offers huge potential to influence product characteristics on demand, and produce designer carbon materials. Future uses of these hydrochars may range from innovative materials to soil amelioration, nutrient conservation via intelligent waste stream management and the increase of carbon stock in degraded soils.

Water repellency in sandy luvisols under different forest transformation stages in northeast Germany

Soil water repellency can adversely affect soil hydrological properties, reduce infiltration capacity and induce preferential flow, surface runoff and erosion. Although primarily described from semiarid and Mediterranean climates, it is also a concern in forest sites under the humid climatic conditions of central Europe. The objective of this study was to characterize the water repellency on geologically comparable forest sites with different stand ages and tree species in terms of the effects of forest transformation upon soil physical properties. The investigated forest site called “Kahlenberg” (50 km northeast of Berlin) contains populations of Pinus sylvestris and Fagus sylvatica of different ages and proportions of single tree species. For the characterization of water repellency, the water drop penetration time (WDPT) test, for determining the persistence of water repellency, and the ethanol percentage (EP) test, which measures the severity or degree of water repellency, were carried out using soil samples from four forest plots and different soil depths (0–160 cm). “Potential” water repellencies were determined after 3-day oven-drying at 45 °C. For two plots, the “actual” water repellency with field moist soil samples was also measured using the WDPT test. The WDPT test revealed a significant proportion of severely and extremely hydrophobic samples in the upper 10 cm of the soil profile for all plots, whereas the persistence of repellency decreased with increasing soil depth. Soil organic matter contents and measured WDPT gave a positive linear correlation with r=0.73. Maximum measured ethanol percentages were 30% and restricted to the upper 5 cm of the soil profiles. The correlation of the organic matter content with EP was r=0.83. For all plots, the EP exhibited a shallower depth distribution than the WDPT. The two plots with pure pine and beech stands exhibited relatively low water repellencies, compared to the plots with mixed tree populations. This corresponds to a higher proportion of mor-type humus and a greater thickness of the humose topsoil at mixed stands compared to the pure pine and beech sites.

Veränderung von Humusform, -vorrat und -verteilung im Zuge von Waldumbau-Maßnahmen im Nordostdeutschen Tiefland

Zusammenfassung:Der Beitrag befasst sich mit den Auswirkungen von Waldumbau-Maßnahmen auf die Humusökologie im nordostdeutschen Tiefland. Untersuchungsobjekt ist eine Chronosequenz bestehend aus einem 84-jährigen Kiefern-Reinbestand (K 75 R), zwei Kiefernbeständen mit unterschiedlich altem Buchen-Voranbau (K 74 Mi und K 75 Mi) und einem 91-jährigen Buchenbestand (K 86). Entlang von Transekten wurden auf allen vier Standorten Humusprofile angelegt, bei denen über 400 Humusziegel (Auflage und A-Horizont) freigelegt und mittels feldbodenkundlicher Methoden charakterisiert wurden. Horizontspezifisch wurden bis 1,60 m Bodentiefe zudem die Tiefengradienten der Verteilung organischer Substanz analysiert. Bei gleichzeitiger Abnahme der Humusauflagen-Mächtigkeit (Tab. 2) innerhalb der Chronosequenz lässt sich ein Wandel von moderartigen Humusformen hin zu mullartigen Humusformen belegen (Abb. 1). Darüber hinaus nehmen bei zunehmendem Umbaualter die Humusvorräte kontinuierlich ab (Abb. 3). Hervorzuheben ist neben dem Humusvorrat dessen prozentuale Verteilung zwischen Auflage und Mineralboden. Die Reinbestände zeigen diesbezüglich ähnliche Größenordnung. Demgegenüber charakterisiert die Mischbestände eine nach Waldumbau initiale Humusakkumulation in der Auflage, was auf eine vorübergehende räumliche und zeitliche Entkopplung des C-Kreislaufs deutet. Humusformenwandel und C-Vorräte werden im Literaturvergleich diskutiert. Schließlich werden denkbare Szenarien mit Blick auf die vertikale Humusverteilung im Boden für weitere im Untersuchungsgebiet praxisrelevante Umbau-Baumarten aufgezeigt (Abb. 5).Summary:The purpose of the present survey was to describe the effects of forest transformation on humus ecology in north-eastern lowlands of Germany. A chronosequence was developed from four stands: one pure Scots pine experimental plot (K 75 R, 84 years old), two Scots pine stands with a beech understory (K 74 Mi, 34 years old and K 75 Mi, 57 years old) and a beech stand (K 86) with an age of 91 years. Sections were set up at each site along which more than 400 humus bricks were characterized. Additionally, the carbon content in the mineral soil horizon was analyzed down to a depth of 1.6 m. Within the chronosequence the humus layer decreased in thickness and the humus form shifted from mor to mor-like mull and oligomull. Furthermore, a continuous decrease in humus stock and in the vertical distribution of soil organic matter between the storage in the litter layer and the storage in the mineral soil was observed. The phenomena were also found in the pure stands in similar dimensions. In contrast, the stands with the beech understorey show an initial humus accumulation in the litter layer. This phenomenon seems to indicate temporal variation and spatial heterogeneity in humus disintegration in the transformed mixed stands.The causes of the changes in humus form and humus stock are discussed. Scenarios are postulated for vertical soil organic matter distribution when by different tree species are planted during forest transformation.

Production of bioenergy in post-mining landscapes in Lusatia: Perspectives and challenges for alternative landuse systems

Abstract Since the German reunification in 1990, lignite production in the Lusatian mining district has significantly decreased as a result of substantial economic and structural changes. This development coincides with efforts by the government of the state of Brandenburg to enhance the production of biomass on set-aside arable and mining land for energy transformation purposes. In this context the goal is that a share of 3% of the primary energy consumption should come from biomass. As part of the on-going recultivation activities in the post-mining landscapes, short-rotation tree plantations as a special form of energy forests have recently come into focus. Thus, in 1995 a 2.5 ha short-rotation plantation was established on clayed-sandy, nutrient-poor substrates in the Lusatian mining area Welzow-Sud in order to study the ecological potential of fast-growing tree species under the prevailing site conditions. Even under unfavourable soil conditions with a low N and P supply, above-ground biomass production ranged from 2.5 to 11.7 tons dry matter per hectare. Three-year-old plants of fast growing tree species like poplar, willow, and aspen were marked by low mean N (5.3 mg g−1), Cl (113 μg g−1), Cd (0.8 μg−1) and Pb (0.5 μg g−1) contents. Therefore, this material is a most favourable biofuel. For the biomass accumulated within this 3-year period a calorific value of 30 000 MJ ha−1 a−1 has been calculated. The ash content of 2.4% allows this material to be used for amelioration purposes. This recycling approach guarantees balanced phosphorus, calcium, and magnesium supply. To maintain adequate site productivity only for nitrogen and potassium, a compensatory fertilization is required.

Transformations of Modern Infrastructure Planning in Rural Regions: The Case of Water Infrastructures in Brandenburg, Germany

Despite profound transformations of spatial development patterns, the “modern infrastructure ideal” of universal and standardized supply with infrastructure services continues to play an important role in discussions on the future of rural infrastructures in shrinking regions of East Germany. Regional planners have reacted to current demographic, socio-economic and environmental transformations by scrutinizing infrastructure standards, but have only begun to reflect upon enhancing the flexibility of infrastructure systems themselves. Until recently, infrastructure planning was treated as a more or less technical and economic problem, without taking into proper account regional specificities and local non-expert knowledge. This paper suggests that flexible, regionally specific and participatory approaches may offer opportunities for innovative and sustainable planning solutions also applicable beyond the infrastructure sector. Referring to the difficult case of the transformation of water supply and waste water disposal systems of Brandenburg in north-eastern Germany, the paper discusses (1) the mismatch between established infrastructure-related planning rationales and current planning problems and (2) potential guidelines that may be constitutive for sustainable water infrastructure planning in the future. These guidelines lead to more general reflections on how infrastructure planning may be conceptualized in view of transforming demographic, environmental and socio-economic conditions.

Impacts of soil additives on crop yield and C-sequestration in post mine substrates of Lusatia, Germany.

Abstract Opencast lignite mining in the Lusatia region of Germany has resulted in large scale landscape disturbances, which require suitable recultivation techniques in order to promote plant growth and establishment in the remaining nutrient-poor substrates with low water-holding capacity. Thus, the effects of two commercial soil additives (CSA), a hydrophilic polymer mixed with volcanic rock flour and bentonite (a-CSA), and digester solids from biogas plants enriched with humic acids and bentonite (b-CSA), on soil organic carbon (SOC) storage, plant yields and root biomass were assessed after cultivating perennial crops (Dactylis glomerata L.) in monoculture and Helianthus annuus L.-Brassica napus L. in crop rotation systems. The CSA were incorporated into the top 20 cm soil depth using a rotary spader. The results indicated that a-CSA led to a significant increase in plant yield during the first year, and improved root biomass in the following year. As a result, SOC stocks increased, especially in the 0–10 cm soil layer. No significant sequestration of additional SOC was observed on b-CSA-amended plots at the end of both years. Bulk density values decreased in all treatments under the monoculture system. It can be concluded that application of a-CSA enhanced soil water availability for plant uptake and consequently promoted plant growth and organic carbon sequestration. The relative enrichment of organic matter without effects on water-holding capacities of b-CSA treatments suggested that it was not suitable for rapid land reclamation.

Impact of Commercial Soil Additives on Microbial Activity and Carbon Isotopic Characteristics of Recultivated Post Lignite Mine Soils

The impact of commercial soil additives (CSA) on post lignite mine soils was assessed after 14 months of field application by evaluating the changes in microbial respiration, the respiratory quotient and the isotopic signature of microbial respired CO2-C. Soil samples were randomly collected from 0 to 5 cm depths from: (1) tilled plots amended with polyacrylate hydrophilic polymer, mixed with zeolithes and bentonite (a-CSA) at 5,000 kg ha−1 dry mass; (2) tilled plots amended with a near-natural digester compost enriched with mineral additives, bentonite and synthesized humic acids (b-CSA) at 10,000 kg ha−1 dry mass; (3) plots tilled and without amendment (control), and (4) plots without tillage and amendment. All plots were seeded with orchard grass (Dactilus glomerata, L.). Soil microbial basal respiration was low and not significantly affected by the treatments presumably, due to low availability of CSA for microbial metabolism. Soil microbial respiration, respiratory quotients and 13C isotopic characteristics of the respired CO2 followed a similar trend for all treatments throughout the incubation period and was not significantly different between a-CSA and b-CSA amended plots compared to the control and untilled plots. The results indicate that the current soil microbial communities have similar eco-physiology and substrate utilisation patterns, and may have met their metabolic requirements mainly from the inherent and recent organic matter input from the vegetation cover. This may be due to the recalcitrant nature of the CSAs or the recommended application rates being too low to affect any significant short-term biochemical impact on these recultivated soils in early stages of development.

Klimawandel und Wasserhaushalt

Die kostengunstige Deckung des Wasserbedarfs der Nutzer bei gleichzeitiger Erhaltung der Okosystemfunktionen von Gewassern stellt eine stetig zu erfullende Aufgabe der Wasserwirtschaft dar. Eine nachhaltige Bewirtschaftung hoch beanspruchter Wasserressourcen-Systeme ist dabei nur mOglich, wenn fortlaufend solche Methoden und Verfahren evaluiert und weiterentwickelt werden, die Veranderungen und Anpassungen des Wasserwirtschaftssystems erlauben. Es gilt, Wasserdargebot und Wasserbedarf durch dargebotsund/ oder bedarfsorientierte Einflussnahmen unter minimalen Kosten bzw. bei maximaler Nachhaltigkeit in ubereinstimmung zu bringen (Grunewald 2008a; Abb. 2-1).

A submerged pine forest from the early Holocene in the Mecklenburg Lake District, northern Germany

(1) GFZ German Research Centre for Geosciences, Potsdam, Germany (kaiserk@gfz-potsdam.de), (2) Nature Park Stechlin-Ruppiner Land, Menz, Germany, (3) University of Potsdam, Institute of Earthand Environmental Science, Potsdam, Germany, (4) University of Greifswald, Institute of Geography and Geology, Greifswald, Germany, (5) University of Greifswald, Institute of Botany and Landscape Ecology, Greifswald, Germany, (6) Müritzeum, Waren (Müritz), Germany, (7) Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), Berlin, Germany, (8) Nature and Biodiversity Conservation Union (NABU), Berlin, Germany

Introduction: A Critical Appraisal of Major Water Engineering Projects and the Need for Interdisciplinary Approaches

Water touches every aspect of human existence on planet earth. While this notion may be regarded as a triviality, it nevertheless has highly complex consequences. Water as a georesource is subject to many pressures due to its multiple functions that go far beyond its role as the fundamental basis of organic life. For instance, antagonistic social, economic and ecological demands meet to form the “water-energy-food” nexus. Rising population numbers, changing lifestyles and climate change have substantial impacts on water resources and aquatic ecosystems. Furthermore, water is a factor in peace among nations: water can be both a source of controversy and of cooperation. The “hidden core” of many international conflicts can be regarded as disputes over the access to water.