Characteristics of ash and particle emissions during bubbling fluidised bed combustion of three types of residual forest biomass

Granulated biomass fly ash coupled with fenton process for pulp and paper wastewater treatment

The work describes the combination of granulated biomass fly ash (G_BFA) with Fenton process to enhance the removal of adsorbable organic halides (AOX) from pulp bleaching wastewater. At optimal operating conditions, wastewater's chemical and biochemical oxygen demand (COD and BOD₅, respectively) and colour were also quantified, and operating cost of treatment assessed. For the first time, raw pulp bleaching wastewater was used to granulate BFA, instead of water, reducing the water footprint of the treatment. Five wastewater treatment setups were studied: (i) conventional Fenton process; (ii) G_BFA application; (iii) simultaneous application of G_BFA and Fenton process; (iv) sequential treatment by G_BFA followed by Fenton process; (v) sequential treatment by Fenton process followed by G_BFA. The latter yielded the highest AOX removal (60-70%), whilst COD was also reduced (≈15%) and wastewater biodegradability (BOD₅/COD) was enhanced from 0.075 to a maximum of 0.134. Another positive feature of the proposed solution was that G_BFA were successfully recovered and reused without regeneration, yielding similar AOX removal compared with fresh G_BFA. The operating cost of removing 1 g of AOX from the pulp bleaching wastewater by the optimal treatment setup (60-70% removal of AOX) was 14-26% lower than the operating cost of conducting Fenton process alone (50% removal of AOX).

Insights for the Valorization of Biomass from Portuguese Invasive Acacia spp. in a Biorefinery Perspective

Acacia spp. are widespread all over the Portuguese territory, representing a threat to local biodiversity and to the productivity of the forest sector. The measures adopted in some countries for their eradication or to control their propagation are expensive, have been considered unfeasible from practical and economical perspectives, and have generated large amounts of residue that must be valorized in a sustainable way. This review brings together information on the valorization of bark, wood, leaves, flowers, pods, seeds, roots, and exudates from Acacia spp., through the production of high-value bioactive extracts (e.g., antioxidant, antimicrobial, anti-inflammatory, antidiabetic, antiviral, anthelmintic, or pesticidal agents, suitable to be explored by pharmaceutical, nutraceutical, cosmetics, and food and feed industries), its incorporation in innovative materials (e.g., polymers and composites, nanomaterials, low-cost adsorbents), as well as through the application of advanced thermochemical processes (e.g., flash pyrolysis) and pre-treatments to decompose biomass in its structural components, regarding the production of biofuels along with valuable chemicals derived from cellulose, hemicellulose, and lignin. The knowledge of this research is important to encourage an efficient and sustainable valorization of Acacia spp. within a biorefinery concept, which can bring a significant economic return from the valorization of these residues, simultaneously contributing to forest cleaning and management, to reduce the risk of fires, and to improve the social-economic development of rural areas.

Human health risk and potential environmental damage of organic and conventional Nicotiana tobaccum production

Tobacco is the most widespread non-food crop in the world. In Brazil, tobacco cultivation is one of the main commodities of the southern region. However, its production is associated with environmental impacts and risks to human health, which have yet to be quantified. This paper uses midpoint and endpoint life cycle assessment (LCA) to analyze the potential environmental damage and human health risk associated with agricultural production of conventional Virginia (CV), organic Virginia (OV), and Burley (BU) tobacco varieties. Organic tobacco production substitutes synthetic fertilizers and pesticides with organic compounds in the cropping stage. The results show that for one ton of dried tobacco, BU, CV, and OV emit 1,610, 1,426, and 1,091 kg CO2 eq, respectively. For organic production, greater impacts are linked to the land use (LU) impact category. The endpoint results showed that OV production resulted in a higher potential for human and environmental damage than BU and CV. The drying of green OV and CV tobacco requires the burning of firewood, which emits high levels of particulate matter and is associated with human health (HH) damage. Overall, the HH damage category accounts for 68%, 82%, and 78% of the total score points associated with the production of BU, CV, and OV.

Efficiency of the Air-Pollution Control System of a Lead-Acid-Battery Recycling Industry

The air-pollution control system of a lead-acid-battery recycling industry was studied. The system comprised two streams with gravity settlers followed by filter bags for the factory indoor air and the metal-recycling furnace, respectively. Efficiency in particle removal according to mass was found to be 99.91%. Moreover, filter bags and dust from the gravity settlers were analyzed for heavy metals by Wavelength Dispersive X-Ray Fluorescence. The results showed high concentrations of Pb and Na in all cases. In the filter bag samples from the indoor atmosphere stream, Ca, Cu, Fe, and Al were found in concentrations higher than that in the filter bag samples from the furnace stream. The opposite was found for Na. Tl and K were only found in furnace stream bag filters. The elemental concentration of the dust from the furnace fumes stream contained mainly Fe, Na, Cd, Pb, Sb, and Cl, while the indoor main stream contained mainly P, Fe, Na, Pb, and Sb. In all cases, impurities of Nd, Ni, Rb, Sr, Th, Hg, and Bi were found. The high efficiency of the air-pollution control system in particle removal shows that a considerable reduction in emissions was achieved.

Accelerated carbonation of wood combustion ash for CO2 removal from gaseous streams and storage in solid form

In this work, ash generated by the combustion of wood in a central heating plant was used to remove and permanently store by accelerated carbonation CO₂ contained in a gas mixture simulating biogas. The process was studied as an alternative treatment to the ones currently available on the market for biogas upgrading. The process was investigated at laboratory scale by setting up a facility for directly contacting the wood ash and the synthetic biogas in a fixed bed reactor. The process was able to completely remove CO₂ during its initial phase. After about 30 h, CO₂ started to appear again in the outlet stream and its concentration rapidly increased. The specific CO₂ uptake achieved in solid carbonate form was of about 200 g/kg of dry wood ash. This value is an order of magnitude higher than the ones found for waste incineration bottom ash carrying out similar experiments. The difference was ascribed to the physicochemical properties of the ash, characterized by a fine particle size (d₅₀ < 0.2 mm) and high content of reactive phases with CO₂ (e.g., Ca hydroxides). The leaching behavior of the wood ash was examined before and after the accelerated carbonation process showing that the release of several elements was lower after the treatment; Ba leaching in particular decreased by over two orders of magnitude. However, the release of the critical elements for the management of this type of residues (especially Cr and sulfates) appeared not to be significantly affected, while V leaching increased.