Barriers to success: A technical review on the limits and possible future roles of small scale gasifiers

Literature and manuals refer to biomass gasification as one of the most efficient processes for power generation, highlighting features, such as residual biomass use, distributed generation and carbon sequestration, that perfectly incorporate gasification into circular economies and sustainable development goals. Despite these features, small scale applications struggle to succeed as a leading solution for sustainable development. The aim of this review is to investigate the existing technological barriers that limit the spreading of biomass gasification from a socio-technical point of view. The review outlines how existing technologies originated from under feed-in-tariff regimes and highlights where the current design goals strongly differ from what will be needed in the near future. Relevant market-ready small-scale gasification systems are analyzed under this lens, leading to an analysis of the reactor and filtration design. To help understand the economical sustainability of these plants, an analysis of the influence of capital expenditures and operating expenditures on the return of investment is included in the discussion. Finally, a literature review on prototypes and pre-market reactors is used as a basis for spotting the characteristics of the system that will likely resolve issues around fuel flexibility, cost efficiency and load variability

Energy cost and parmesan cheese. An overview in the different energy fluxes needed to produce a parmesan wheel

Agriculture is responsible for up to 30% of the greenhouse gases emission, and cattle breeding is the main contributor making up almost 10% of the total. For this reason, this sector is a key player toward a complete decarbonization. To take the proper action to reduce climate impact of cattle breeding, it is necessary to know the energy requirements of the industry. This work focuses on the energy mapping of a parmesan cheese production, with reference to an agricultural company situated in Modena province with about six hundred animals. Knowing the electrical and thermal energy requirements to produce a wheel of cheese gives the possibility to the farmers to identify and reduce the energy wastage as well as starting the implementation of a strategy for fossil fuel substitution. In this study, a comprehensive monitoring campaign is presented together with the proposal of some possible improvements. The analysis showed that, considering the actual situation, about 64 kWh of electrical energy and 94 kWh of thermal energy are needed to produce a parmesan cheese wheel, while the fuel used to feed the agricultural machinery (e.g., tractors) accounts for around 174 kWh. In this context, the implementation of biogas and solar photovoltaic can greatly contribute to reduce the dependence on fossil fuels

Domestic heating: Can hemp-hurd derived pellet be an alternative?

Among the renewable sources, residual woody biomass from agricultural crops is becoming of great interest due to its lower environmental impact and one of the most growing agricultural sector, of the last decade, is the hemp industry which generates several kind of byproducts. In this paper, a blend of 50% of hemp-hurd and 50% of fir sawdust was pulverized and pelletized. The pellets were burned into a domestic pellet stove (9 kWth maximum nominal thermal power output) at different biomass flowrates. To compare results with a commercial-grade pellet, the tests were repeated by fueling the same stove with A2-grade pellets. Results shown that the pellet mixture 50/50 of fir sawdust and hemp-hurd is suitable for the commercial pellet stove used and that the slightly higher amount of ashes (2.7%), compared to pellet A2 (<1.2%), can be handled by the self-cleaning fire chamber. Comparable results were also obtained in regards with the stove global efficiency which ranged from 90.8-92.3% for the hemp pellets and 91-94% for the A2. A significant difference was noted in the biomass flowrate where, during the tests with hemp-hurd pellets a lower value was obtained (-20%) compared to A2. This resulted into lower power input in the stove and lower performances at the same nominal power output

Thermal Stabilization of Digesters of Biogas Plants by Means of Optimization of the Surface Radiative Properties of the Gasometer Domes

A new incentive scheme for power generation from biogas is favoring in Italy the construction of small plants. These ones, however, have poorer financial viability and biological stability than larger plants. In order to ensure adequate performance and a reasonable payback period it is therefore essential that every aspect of their operations is carefully designed. In this respect, summer overheating of anaerobic digesters due to solar gains must be prevented. A solution relies upon the implementation of a ‘cool’ gasometer dome with properly chosen solar reflectance, whose effectiveness was assessed through the use of a calculation code specifically built and validated by comparison with experimental data

Preliminary Investigation of Possible Biochar Use as Carbon Source in Polyacrylonitrile Electrospun Fiber Production

Electrospinning with consequent thermal treatment consists in a carbon fiber production method that spins a polymer solution to create fibers with diameters around a few hundred nanome-ters. The thermal treatments are used for the cyclization and then carbonization of the material at 1700◦C for one hour. The unique structure of micro-and nano-carbon fibers makes them a promis-ing material for various applications ranging from future battery designs to filtration. This work investigated the possibility of using milled gasification biochar, derived from a 20 kW fixed-bed gasifier fueled with vine pruning pellets, as an addictive in the preparation of electrospinning solu-tions. This study outlined that solvent cleaning and the consequent wet-milling and 32 µm sifting are fundamental passages for biochar preparation. Four different polyacrylonitrile-biochar shares were tested ranging from pure polymer to 50–50% solutions. The resulting fibers were analyzed via scanning electron microscopy, and energy-dispersive X-ray and infrared spectroscopy. Results from the morphological analysis showed that biochar grains dispersed themselves well among the fiber mat in all the proposed shares. All the tested solutions, once carbonized, exceeded 97%wt. of carbon content. At higher carbonization temperatures, the inorganic compounds naturally showing in biochar such as potassium and calcium disappeared, resulting in an almost carbon-pure fiber matrix with biochar grains in between

Experimental investigation of chestnut shells gasification

Fossil fuels substitution with renewable energy sources is necessary for an effective decarbonization. Biomass can represent a valid alternative to fossil fuels, reducing greenhouse gas emissions. Furthermore, bioenergy generation avoids costs and problems related to biomass disposal. This study presents the energetic valorisation of chestnut shells, a byproduct of the chestnut transformation processes. Through a thermo-conversion system based on gasification, this material was considered not as a waste, but as a resource to be exploited to produce bioenergy and biochar. The fuel gas produced through the gasification process can partially replace the LPG currently used to meet the energy required for the brulage and steam peeling processes. Experimental gasification tests were carried out to evaluate this biomass by means of a laboratory scale micro-gasifier (Imbert downdraft type). Chestnut shells were pelletized with a pelletizer machine to avoid the bridging effect inside the gasifier and increase its energy density. The fuel gas obtained was sampled and analyzed to measure its composition and HHV. In addition, the gasification efficiency was calculated obtaining a value of 70%, a result in line with the ones obtained with higher quality biomasses

Experimental investigation of moisture influence on biochar and biochar-soil blends thermophysical properties

Biochar is a carbonaceous and porous material obtained through pyrolysis or gasification. It can be extremely valuable as soil amendment since it increases the organic matter content and fertility, the microbial activity, the water retention, and the crop yields. Moreover, biochar soil application has the potential for long-term carbon sequestration which makes its application to soil interesting even outside agricultural crops. In recent years, the study of the variation of the thermophysical properties of the soil induced by mixing with biochar has attracted interest. In this work, the effect of the water content on thermal conductivity of biochar was investigated by means of the guarded hot plate apparatus λ-Meter EP500e. The same procedure was applied to various mixtures of biochar and soil. Furthermore, the specific heat was measured in order to obtain the thermal diffusivity in the various conditions through a calorimeter. Solar reflectance was also measured following the ASTM C1549 using a solar spectrum reflectometer SSR-ER. The obtained thermophysical properties can be used for the evaluation of the temperature trend of soil at different depths during the seasonal variations

A technical-economic analysis of integrating vine prunings energy conversion systems for CHP production in local wineries

This study proposes the energy conversion of vine prunings to supply energy to local wineries, with a focus on the Riunite & CIV branch winery located in Carpi (Modena, Italy), exploring the possibility of generating both electricity and heat through biomass gasification. A Matlab-Simulink model is used to evaluate the energy savings that can be achieved when an energy storage system is coupled with the combined heat and power generation system. Within this context, the results showed that it is possible to save approximate to 60% of the thermal energy demanded by the winery. However, the economic viability of the project is hindered by high investment and operation costs. DPB is strongly affected by the cost of biomass and the energy prices, resulting in a profitable investment for electricity prices higher than 0.30(sic)> 0.57 euro/kWh according to the different scenarios investigated

Airborne pathogens diffusion: A comparison between tracer gas and pigmented aerosols for indoor environment analysis

The evaluation of airborne pathogens diffusion is a crucial practice in preventing airborne diseases like COVID-19, especially in indoor environments. Through this transmission route, pathogens can be carried by droplets, droplet nuclei and aerosols and be conveyed over long distances. Therefore, understanding their diffusion is vital for prevention and curbing disease transmission. There are different techniques used for this purpose, and one of the most common is the utilization of tracer gas, however, it has limitations such as the difference in size between the gas molecules and the respiratory droplets, as well as its incapability to take into account evaporation. For this reason, a new method for evaluating the diffusion of respiratory droplets has been developed. This approach involves the use of an ultrasonic emitter to release and disperse pigmented aerosols, and a colorimeter for the following quantitative evaluation. A comparison with the tracer gas technique has been carried out, showing for the pigmented aerosols methodology a response that is dependent on different relative humidity conditions, while there is no clear difference in the dispersion of tracer gas at high or low humidity