• Energy Research

AbstractThe density of wood is a key indicator of the carbon investment strategies of trees, impacting productivity and carbon storage. Despite its importance, the global variation in wood density and its environmental controls remain poorly understood, preventing accurate predictions of global forest carbon stocks. Here we analyse information from 1.1 million forest inventory plots alongside wood density data from 10,703 tree species to create a spatially explicit understanding of the global wood density distribution and its drivers. Our findings reveal a pronounced latitudinal gradient, with wood in tropical forests being up to 30% denser than that in boreal forests. In both angiosperms and gymnosperms, hydrothermal conditions represented by annual mean temperature and soil moisture emerged as the primary factors influencing the variation in wood density globally. This indicates similar environmental filters and evolutionary adaptations among distinct plant groups, underscoring the essential role of abiotic factors in determining wood density in forest ecosystems. Additionally, our study highlights the prominent role of disturbance, such as human modification and fire risk, in influencing wood density at more local scales. Factoring in the spatial variation of wood density notably changes the estimates of forest carbon stocks, leading to differences of up to 21% within biomes. Therefore, our research contributes to a deeper understanding of terrestrial biomass distribution and how environmental changes and disturbances impact forest ecosystems.

We conducted a feasibility study in Indochina (Cambodia, Laos, Myanmar, Thailand, and Vietnam) with the aim of promoting biomass and bioenergy markets, technology transfer, rural development, and income generation. Policy development is guided by the International Union of Forest Research Institutions (IUFRO) Task Force “Sustainable Forest Bioenergy Network”. In this paper, we highlight the achievements up to now and present results of a multi-stakeholder questionnaire in combination with a quantitative analysis of the National Bioenergy Development Plans (NBDPs). We found a gap between official documents and working group assessments. NBDPs are focused on the market development, technology transfer, and funding possibilities of a regional bioenergy strategy, while the respondents of a questionnaire (working groups) favored more altruistic goals, i.e., sustainable resource management, environmental protection and climate change mitigation, generation of rural income, and community involvement, etc. We therefore suggest the following measures to ensure regulations that support the original aims of the network (climate change mitigation, poverty alleviation, sustainable resource use, and diversification of energy generation): (i) Consideration of science-based evidence for drafting bioenergy policies, particularly in the field of biomass production and harvesting; (ii) invitation of stakeholders representing rural communities to participate in this process; (iii) development of sustainability criteria; (iv) feedback cycles ensuring more intensive discussion of policy drafts; (v) association of an international board of experts to provide scientifically sound feedback and input; and (vi) establishment of a local demonstration region, containing various steps in the biomass/bioenergy supply chain including transboundary collaboration in the ACMECS region.

Iron and steel plants producing steel via the blast furnace-basic oxygen furnace (BF-BOF) route constitute among the largest single point CO2 emitters within the European Union (EU). As the iron ore reduction process in the blast furnace is fully dependent on carbon mainly supplied by coal and coke, bioenergy is the only renewable that presents a possibility for their partial substitution. Using the BeWhere model, this work optimised the mobilization and use of biomass resources within the EU in order to identify the opportunities that bioenergy can bring to the 30 operating BF-BOF plants.\ud \ud \ud \ud The results demonstrate competition for the available biomass resources within existing industries and economically unappealing prices of the bio-based fuels. A carbon dioxide price of 60 € t−1 is required to substitute 20% of the CO2 emissions from the fossil fuels use, while a price of 140 € t−1 is needed to reach the maximum potential of 42%. The possibility to use organic wastes to produce hydrochar would not enhance the maximum emission reduction potential, but it would broaden the available feedstock during the low levels of substitution.\ud \ud \ud \ud The scope for bioenergy integration is different for each plant and so consideration of its deployment should be treated individually. Therefore, the EU-ETS (Emission Trading System) may not be the best policy tool for bioenergy as an emission reduction strategy for the iron and steel industry, as it does not differentiate between the opportunities across the different steel plants and creates additional costs for the already struggling European steel industry.

Bioenergy plays an important role in mitigating dangerous climate change and will therefore most likely have to further expand substantially. With 50% of the global population living in urban areas, cities are transforming into hotspots for future sustainable energy systems in the context of a low-carbon society. Bioenergy feedstock from urban forests could contribute substantially to low-carbon energy supply, yet urban ecosystems also provide other services that have to be balanced against future energy needs. This study conducts a geo-spatial analysis of urban forests with respect to its potential of increasing feedstock production for urban bioenergy generation. At the same time, social and environmental constraints are considered and co-benefits discussed. In order to test the wider applicability of the methodology, the Vienna Woods Biosphere Reserve is chosen as a case study to determine the feedstock potential for local bioenergy provided to Viennese households. The theoretical biomass potential is modeled using biophysical growth and yield tables for individual tree species and then compared to the existing production area using GIS tools. Results show that the biomass use within the biosphere reserve can be increased by about 60% without violating any national or international law that protects multiple ecosystem services provided by the reserve, nor sustainability criteria of forest management. This indicates a high potential of peri-urban forest ecosystems to contribute to urban resilience – i.e. with respect to energy security and emissions reduction. The study concludes that urban forests require sensible management in order to minimize conflicts of multiple environmental, economic and social uses of the area.

La biomasse forestière est un indicateur essentiel pour la surveillance des écosystèmes et du climat de la Terre. Il s'agit d'une contribution essentielle à la comptabilisation des gaz à effet de serre, à l'estimation des pertes de carbone et de la dégradation des forêts, à l'évaluation du potentiel des énergies renouvelables et à l'élaboration de politiques d'atténuation du changement climatique telles que REDD+, entre autres. La cartographie mur à mur de la biomasse aérienne (AGB) est maintenant possible avec la télédétection par satellite (RS). Cependant, les méthodes RS nécessitent des données in situ existantes, à jour, fiables, représentatives et comparables pour l'étalonnage et la validation. Nous présentons ici l'initiative Forest Observation System (Fos), une coopération internationale visant à établir et à maintenir une base de données mondiale sur la biomasse forestière in situ. Les estimations de la hauteur de l'AGB et de la canopée avec leurs incertitudes associées sont dérivées à une échelle de 0,25 ha à partir de mesures sur le terrain effectuées dans des parcelles de recherche permanentes à travers les forêts du monde. Toutes les estimations des placettes sont géolocalisées et ont une taille qui permet une comparaison directe avec de nombreuses mesures RS. Le Fos offre le potentiel d'améliorer la précision des produits de la biomasse à base de RS tout en développant de nouvelles synergies entre la RS et les communautés de recherche sur les écosystèmes terrestres. La biomasa forestal es un indicador esencial para monitorear los ecosistemas y el clima de la Tierra. Es un insumo crítico para la contabilidad de gases de efecto invernadero, la estimación de las pérdidas de carbono y la degradación forestal, la evaluación del potencial de energía renovable y para el desarrollo de políticas de mitigación del cambio climático como REDD+, entre otras. El mapeo de pared a pared de la biomasa sobre el suelo (AGB) ahora es posible con la teledetección satelital (RS). Sin embargo, los métodos de RS requieren datos in situ existentes, actualizados, confiables, representativos y comparables para la calibración y validación. Aquí, presentamos la iniciativa del Sistema de Observación Forestal (FOS), una cooperación internacional para establecer y mantener una base de datos global de biomasa forestal in situ. Las estimaciones de altura de AGB y dosel con sus incertidumbres asociadas se derivan a una escala de 0,25 ha a partir de mediciones de campo realizadas en parcelas de investigación permanentes en los bosques del mundo. Todas las estimaciones de parcelas están geolocalizadas y tienen un tamaño que permite la comparación directa con muchas mediciones de RS. El FOS ofrece el potencial de mejorar la precisión de los productos de biomasa basados en RS al tiempo que desarrolla nuevas sinergias entre las comunidades de investigación de ecosistemas basados en RS y en tierra. Forest biomass is an essential indicator for monitoring the Earth's ecosystems and climate. It is a critical input to greenhouse gas accounting, estimation of carbon losses and forest degradation, assessment of renewable energy potential, and for developing climate change mitigation policies such as REDD+, among others. Wall-to-wall mapping of aboveground biomass (AGB) is now possible with satellite remote sensing (RS). However, RS methods require extant, up-to-date, reliable, representative and comparable in situ data for calibration and validation. Here, we present the Forest Observation System (FOS) initiative, an international cooperation to establish and maintain a global in situ forest biomass database. AGB and canopy height estimates with their associated uncertainties are derived at a 0.25 ha scale from field measurements made in permanent research plots across the world's forests. All plot estimates are geolocated and have a size that allows for direct comparison with many RS measurements. The FOS offers the potential to improve the accuracy of RS-based biomass products while developing new synergies between the RS and ground-based ecosystem research communities. الكتلة الحيوية للغابات هي مؤشر أساسي لرصد النظم الإيكولوجية للأرض ومناخها. وهو مدخل حاسم في المحاسبة المتعلقة بغازات الدفيئة، وتقدير خسائر الكربون وتدهور الغابات، وتقييم إمكانات الطاقة المتجددة، ووضع سياسات للتخفيف من آثار تغير المناخ مثل المبادرة المعززة لخفض الانبعاثات الناجمة عن إزالة الغاباتوتدهورها، من بين أمور أخرى. أصبح من الممكن الآن رسم خرائط من الجدار إلى الجدار للكتلة الحيوية فوق الأرض (AGB) باستخدام الاستشعار عن بعد عبر الأقمار الصناعية (RS). ومع ذلك، تتطلب طرق RS بيانات موجودة وحديثة وموثوقة وتمثيلية وقابلة للمقارنة في الموقع للمعايرة والتحقق من الصحة. نقدم هنا مبادرة نظام مراقبة الغابات، وهو تعاون دولي لإنشاء وصيانة قاعدة بيانات عالمية للكتلة الحيوية للغابات في الموقع. يتم اشتقاق تقديرات ارتفاع AGB والمظلة مع أوجه عدم اليقين المرتبطة بها على مقياس 0.25 هكتار من القياسات الميدانية التي تم إجراؤها في قطع البحث الدائمة عبر غابات العالم. جميع تقديرات المخطط محددة جغرافيًا ولها حجم يسمح بالمقارنة المباشرة مع العديد من قياسات RS. يوفر نظام التشغيل الحر إمكانية تحسين دقة منتجات الكتلة الحيوية القائمة على RS مع تطوير أوجه تآزر جديدة بين RS ومجتمعات أبحاث النظام الإيكولوجي الأرضية.