Economics & Job Creation
“The Employment Situation — August 2021”
“Engineered cells successfully treat cardiovascular and pulmonary disease”
“Inflatable robotic hand gives amputees real-time tactile control”
“Neuroprosthesis restores words to a man with paralysis”
“Turning hazelnut shells into potential renewable energy source”
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Economics & Job Creation
“The Employment Situation – August 2021”
THE EMPLOYMENT SITUATION -- August 2021 Total nonfarm payroll employment rose by 235,000 in August, and the unemployment rate declined by 0.2 percentage point to 5.2 percent, the U.S. Bureau of Labor Statistics reported today. So far this year, monthly job growth has averaged 586,000. In August, notable job gains occurred in professional and business services, transportation and warehousing, private education, manufacturing, and other services. Employment in retail trade declined over the month. This news release presents statistics from two monthly surveys. The household survey measures labor force status, including unemployment, by demographic characteristics. The establishment survey measures nonfarm employment, hours, and earnings by industry. For more information about the concepts and statistical methodology used in these two surveys, see the Technical Note. Household Survey Data The unemployment rate declined by 0.2 percentage point to 5.2 percent in August. The number of unemployed persons edged down to 8.4 million, following a large decrease in July. Both measures are down considerably from their highs at the end of the February-April 2020 recession. However, they remain above their levels prior to the coronavirus (COVID-19) pandemic (3.5 percent and 5.7 million, respectively, in February 2020). (See table A-1. See the box note at the end of this news release for more information about how the household survey and its measures were affected by the coronavirus pandemic.) Among the major worker groups, the unemployment rates for adult men (5.1 percent) and Whites (4.5 percent) declined in August, while the rate for teenagers (11.2 percent) increased. The jobless rates for adult women (4.8 percent), Blacks (8.8 percent), Asians (4.6 percent), and Hispanics (6.4 percent) showed little change over the month. (See tables A-1, A-2, and A-3.) Among the unemployed, the number of permanent job losers declined by 443,000 to 2.5 million in August but is 1.2 million higher than in February 2020. The number of persons on temporary layoff, at 1.3 million, was essentially unchanged in August. This measure is down considerably from the high of 18.0 million in April 2020 but is 502,000 above the February 2020 level. The number of reentrants to the labor force increased by 200,000 in August to 2.5 million. (Reentrants are persons who previously worked but were not in the labor force prior to beginning their job search.) (See table A-11.) The number of long-term unemployed (those jobless for 27 weeks or more) decreased by 246,000 in August to 3.2 million but is 2.1 million higher than in February 2020. These long-term unemployed accounted for 37.4 percent of the total unemployed in August. The number of persons jobless less than 5 weeks, at 2.1 million, was little changed. (See table A-12.) The labor force participation rate, at 61.7 percent in August, was unchanged over the month and has remained within a narrow range of 61.4 percent to 61.7 percent since June 2020. The participation rate is 1.6 percentage points lower than in February 2020. The employment-population ratio, at 58.5 percent, was little changed in August. This measure is up from its low of 51.3 percent in April 2020 but remains below the figure of 61.1 percent in February 2020. (See table A-1.) In August, the number of persons employed part time for economic reasons, at 4.5 million, was essentially unchanged. There were 4.4 million persons in this category in February 2020. These individuals, who would have preferred full-time employment, were working part time because their hours had been reduced or they were unable to find full-time jobs. (See table A-8.) The number of persons not in the labor force who currently want a job declined by 835,000 in August to 5.7 million but remains higher than the level in February 2020 (5.0 million). These individuals were not counted as unemployed because they were not actively looking for work during the last 4 weeks or were unavailable to take a job. (See table A-1.) Among those not in the labor force who wanted a job, the number of persons marginally attached to the labor force, at 1.6 million in August, decreased by 295,000 over the month. These individuals wanted and were available for work and had looked for a job sometime in the prior 12 months but had not looked for work in the 4 weeks preceding the survey. The number of discouraged workers, a subset of the marginally attached who believed that no jobs were available for them, was 392,000 in August, down by 115,000 from the previous month. (See Summary table A.) Household Survey Supplemental Data In August, 13.4 percent of employed persons teleworked because of the coronavirus pandemic, little changed from the prior month. These data refer to employed persons who teleworked or worked at home for pay at some point in the last 4 weeks specifically because of the pandemic. In August, 5.6 million persons reported that they had been unable to work because their employer closed or lost business due to the pandemic--that is, they did not work at all or worked fewer hours at some point in the last 4 weeks due to the pandemic. This measure is up from 5.2 million in July. Among those who reported in August that they were unable to work because of pandemic-related closures or lost business, 13.9 percent received at least some pay from their employer for the hours not worked, up from 9.1 percent in the prior month. Among those not in the labor force in August, 1.5 million persons were prevented from looking for work due to the pandemic, little changed from July. (To be counted as unemployed, by definition, individuals must be either actively looking for work or on temporary layoff.) These supplemental data come from questions added to the household survey beginning in May 2020 to help gauge the effects of the pandemic on the labor market. The data are not seasonally adjusted. Tables with estimates from the supplemental questions for all months are available online at www.bls.gov/cps/effects-of-the-coronavirus-covid-19-pandemic.htm. Establishment Survey Data Total nonfarm payroll employment rose by 235,000 in August, following increases of 1.1 million in July and 962,000 in June. Nonfarm employment has risen by 17.0 million since April 2020 but is down by 5.3 million, or 3.5 percent, from its pre-pandemic level in February 2020. In August, notable job gains occurred in professional and business services, transportation and warehousing, private education, manufacturing, and other services. Employment in retail trade declined over the month. (See table B-1. See the box note at the end of this news release for more information about how the establishment survey and its measures were affected by the coronavirus pandemic.) Employment in professional and business services increased by 74,000 in August. Employment rose in architectural and engineering services (+19,000), computer systems design and related services (+10,000), scientific research and development services (+7,000), and office administrative services (+6,000). Since February 2020, employment in professional and business services is down by 468,000, over half of which is in temporary help services (-262,000). Transportation and warehousing added 53,000 jobs in August, bringing employment in the industry slightly above (+22,000) its pre-pandemic level in February 2020. Employment gains have been led by strong growth in couriers and messengers and in warehousing and storage, which added 20,000 jobs each in August. Air transportation also added jobs (+11,000), while transit and ground passenger transportation--which includes school buses--lost jobs (-8,000). In August, employment increased by 40,000 in private education, declined by 21,000 in state government education, and changed little in local government education (-6,000). In all three industries, these employment changes followed job gains in June and July. August marks the beginning of the traditional back-to-school season. However, recent employment changes are challenging to interpret, as pandemic-related staffing fluctuations in public and private education have distorted the normal seasonal hiring and layoff patterns. Since February 2020, employment is down by 159,000 in private education, by 186,000 in state government education, and by 220,000 in local government education. Manufacturing added 37,000 jobs in August, with gains in motor vehicles and parts (+24,000) and fabricated metal products (+7,000). Employment in manufacturing is down by 378,000 from its pre-pandemic level in February 2020. The other services industry added 37,000 jobs in August, but employment is 189,000 lower than in February 2020. In August, employment rose in personal and laundry services (+19,000) and in repair and maintenance (+9,000). Employment in information increased by 17,000 in August, reflecting a gain in data processing, hosting, and related services (+12,000). Employment in information is down by 150,000 since February 2020. Employment in financial activities rose by 16,000 over the month, with most of the gain occurring in real estate (+11,000). Employment in financial activities is down by 29,000 since February 2020. Mining added 6,000 jobs in August, reflecting a gain in support activities for mining (+4,000). Mining employment has risen by 55,000 since a trough in August 2020 but is 96,000 below a peak in January 2019. Employment in retail trade declined by 29,000 in August, with losses in food and beverage stores (-23,000) and in building material and garden supply stores (-13,000). Retail trade employment is down by 285,000 since February 2020. In August, employment in leisure and hospitality was unchanged, after increasing by an average of 350,000 per month over the prior 6 months. In August, a job gain in arts, entertainment, and recreation (+36,000) was more than offset by a loss in food services and drinking places (-42,000). Employment in leisure and hospitality is down by 1.7 million, or 10.0 percent, since February 2020. In August, employment showed little change in other major industries, including construction, wholesale trade, and health care. Average hourly earnings for all employees on private nonfarm payrolls rose by 17 cents to $30.73 in August, following increases in the prior 4 months. In August, average hourly earnings of private-sector production and nonsupervisory employees rose by 14 cents to $25.99. The data for recent months suggest that the rising demand for labor associated with the recovery from the pandemic may have put upward pressure on wages. However, because average hourly earnings vary widely across industries, the large employment fluctuations since February 2020 complicate the analysis of recent trends in average hourly earnings. (See tables B-3 and B-8.) In August, the average workweek for all employees on private nonfarm payrolls was 34.7 hours for the third consecutive month. In manufacturing, the average workweek fell by 0.2 hour over the month to 40.3 hours, and overtime remained at 3.2 hours. The average workweek for production and nonsupervisory employees on private nonfarm payrolls was unchanged at 34.2 hours. (See tables B-2 and B-7.) The change in total nonfarm payroll employment for June was revised up by 24,000, from +938,000 to +962,000, and the change for July was revised up by 110,000, from +943,000 to +1,053,000. With these revisions, employment in June and July combined is 134,000 higher than previously reported. (Monthly revisions result from additional reports received from businesses and government agencies since the last published estimates and from the recalculation of seasonal factors.) The Employment Situation for September is scheduled to be released on Friday, October 8, 2021, at 8:30 a.m. (ET).
“Engineered cells successfully treat cardiovascular and pulmonary disease”
Scientists at UC San Francisco have shown that gene-edited cellular therapeutics can be used to successfully treat cardiovascular and pulmonary diseases, potentially paving the way for developing less expensive cellular therapies to treat diseases for which there are currently few viable options.
The study, in mice, is the first in the emerging field of regenerative cell therapy to show that products from specially engineered induced pluripotent stem cells called “HIP” cells can successfully be employed to treat major diseases while evading the immune system. The findings subvert the immune response that is a major cause of transplant failure and poses a barrier to using engineered cells as therapy.
“We showed that immune-engineered HIP cells reliably evade immune rejection in mice with different tissue types, a situation similar to the transplantation between unrelated human individuals. This immune evasion was maintained in diseased tissue and tissue with poor blood supply without the use of any immunosuppressive drugs.” said Tobias Deuse, MD, the Julien I.E. Hoffman, M.D. Endowed Chair in Cardiac Surgery and a first author of the study.
Deuse’s research is an example of “living therapeutics,” an emerging pillar of medicine in which treatments are broadly defined as living human and microbial cells that are selected, modified, or engineered to treat or cure disease.
The study appears in Proceedings of the National Academy of Sciences.
“Universal Stem Cells” Avoid Immune Detection
The prospects of generating specialized cells in a dish that can be transplanted into patients to treat various diseases are encouraging, the scientists report. However, the immune system would immediately recognize cells that were recovered from another individual and would reject the cells. Hence, some scientists believe that custom cell therapeutics need to be generated from scratch using a blood sample from every individual patient as starting material.
The research group at UCSF followed a different approach, using gene editing to create ‘universal stem cells’ (named HIP cells) that are not recognized by the immune system and can be used to make “universal cell therapeutics.”
The team tested the ability of these cells to treat three major diseases affecting different organ systems: Peripheral artery disease; chronic obstructive pulmonary disease from alpha1-antitrypsin deficiency; and heart failure, increasingly a global epidemic with more than 5.7 million patients in the United States alone and some 870,000 new cases annually.
The scientists transplanted specialized, immune-engineered HIP cells into mice with each of these conditions and were able to show that the cell therapeutics could alleviate peripheral artery disease in hindlimbs, prevent the development of lung disease in mice with alpha1-antitrypsin deficiency, and alleviate heart failure in mice after myocardial infarction.
To enhance the translational aspect of this proof-of-concept study, the researchers assessed the treatment’s efficacy using standard parameters for human clinical trials focusing on outcome and organ function.
The Promise of an Affordable Option
Deuse, who is also surgical director of the Transcatheter Valve Program and directs Minimally Invasive Cardiac Surgery, plans to explore the potential of these universal stems cells for treating other endocrine and cardiovascular conditions. He noted that, because of the novelty of the approach, a careful and measured introduction into clinical trials will be crucial. Once more is known about human safety, he said, it will be easier to estimate when treatments using HIP cells might be approved and available for patients.
One of the great benefits of this approach, said Deuse, is that the strategy of immune engineering comes with a reasonable price tag. It would make the manufacturing of universal, high-quality cell therapeutics more cost effective, could allow future treatment of larger patient populations, and facilitate access for patients from underserved communities.
“In order for a therapeutic to have a broad impact, it needs to be affordable,” said Deuse. “That’s why we focus so much on immune-engineering and the development of universal cells. Once the costs come down, the access for all patients in need increases.”
“Inflatable robotic hand gives amputees real-time tactile control”
For the more than 5 million people in the world who have undergone an upper-limb amputation, prosthetics have come a long way. Beyond traditional mannequin-like appendages, there is a growing number of commercial neuroprosthetics — highly articulated bionic limbs, engineered to sense a user’s residual muscle signals and robotically mimic their intended motions.
But this high-tech dexterity comes at a price. Neuroprosthetics can cost tens of thousands of dollars and are built around metal skeletons, with electrical motors that can be heavy and rigid.
Now engineers at MIT and Shanghai Jiao Tong University have designed a soft, lightweight, and potentially low-cost neuroprosthetic hand. Amputees who tested the artificial limb performed daily activities, such as zipping a suitcase, pouring a carton of juice, and petting a cat, just as well as — and in some cases better than — those with more rigid neuroprosthetics.
The researchers found the prosthetic, designed with a system for tactile feedback, restored some primitive sensation in a volunteer’s residual limb. The new design is also surprisingly durable, quickly recovering after being struck with a hammer or run over with a car.
The smart hand is soft and elastic, and weighs about half a pound. Its components total around $500 — a fraction of the weight and material cost associated with more rigid smart limbs.
“This is not a product yet, but the performance is already similar or superior to existing neuroprosthetics, which we’re excited about,” says Xuanhe Zhao, professor of mechanical engineering and of civil and environmental engineering at MIT. “There’s huge potential to make this soft prosthetic very low cost, for low-income families who have suffered from amputation.”
Big Hero hand
The team’s pliable new design bears an uncanny resemblance to a certain inflatable robot in the animated film “Big Hero 6.” Like the squishy android, the team’s artificial hand is made from soft, stretchy material — in this case, the commercial elastomer EcoFlex. The prosthetic comprises five balloon-like fingers, each embedded with segments of fiber, similar to articulated bones in actual fingers. The bendy digits are connected to a 3-D-printed “palm,” shaped like a human hand.
Rather than controlling each finger using mounted electrical motors, as most neuroprosthetics do, the researchers used a simple pneumatic system to precisely inflate fingers and bend them in specific positions. This system, including a small pump and valves, can be worn at the waist, significantly reducing the prosthetic’s weight.
Lin developed a computer model to relate a finger’s desired position to the corresponding pressure a pump would have to apply to achieve that position. Using this model, the team developed a controller that directs the pneumatic system to inflate the fingers, in positions that mimic five common grasps, including pinching two and three fingers together, making a balled-up fist, and cupping the palm.
The pneumatic system receives signals from EMG sensors — electromyography sensors that measure electrical signals generated by motor neurons to control muscles. The sensors are fitted at the prosthetic’s opening, where it attaches to a user’s limb. In this arrangement, the sensors can pick up signals from a residual limb, such as when an amputee imagines making a fist.
The team then used an existing algorithm that “decodes” muscle signals and relates them to common grasp types. They used this algorithm to program the controller for their pneumatic system. When an amputee imagines, for instance, holding a wine glass, the sensors pick up the residual muscle signals, which the controller then translates into corresponding pressures. The pump then applies those pressures to inflate each finger and produce the amputee’s intended grasp.
Going a step further in their design, the researchers looked to enable tactile feedback — a feature that is not incorporated in most commercial neuroprosthetics. To do this, they stitched to each fingertip a pressure sensor, which when touched or squeezed produces an electrical signal proportional to the sensed pressure. Each sensor is wired to a specific location on an amputee’s residual limb, so the user can “feel” when the prosthetic’s thumb is pressed, for example, versus the forefinger.
To test the inflatable hand, the researchers enlisted two volunteers, each with upper-limb amputations. Once outfitted with the neuroprosthetic, the volunteers learned to use it by repeatedly contracting the muscles in their arm while imagining making five common grasps.
After completing this 15-minute training, the volunteers were asked to perform a number of standardized tests to demonstrate manual strength and dexterity. These tasks included stacking checkers, turning pages, writing with a pen, lifting heavy balls, and picking up fragile objects like strawberries and bread. They repeated the same tests using a more rigid, commercially available bionic hand and found that the inflatable prosthetic was as good, or even better, at most tasks, compared to its rigid counterpart.
One volunteer was also able to intuitively use the soft prosthetic in daily activities, for instance to eat food like crackers, cake, and apples, and to handle objects and tools, such as laptops, bottles, hammers, and pliers. This volunteer could also safely manipulate the squishy prosthetic, for instance to shake someone’s hand, touch a flower, and pet a cat.
In a particularly exciting exercise, the researchers blindfolded the volunteer and found he could discern which prosthetic finger they poked and brushed. He was also able to “feel” bottles of different sizes that were placed in the prosthetic hand, and lifted them in response. The team sees these experiments as a promising sign that amputees can regain a form of sensation and real-time control with the inflatable hand.
The team has filed a patent on the design, through MIT, and is working to improve its sensing and range of motion.
“We now have four grasp types. There can be more,” Zhao says. “This design can be improved, with better decoding technology, higher-density myoelectric arrays, and a more compact pump that could be worn on the wrist. We also want to customize the design for mass production, so we can translate soft robotic technology to benefit society.”
“Neuroprosthesis restores words to a man with paralysis”
Researchers at UC San Francisco have successfully developed a “speech neuroprosthesis” that has enabled a man with severe paralysis to communicate in sentences, translating signals from his brain to the vocal tract directly into words that appear as text on a screen.
The achievement, which was developed in collaboration with the first participant of a clinical research trial, builds on more than a decade of effort by UCSF neurosurgeon Edward Chang, MD, to develop a technology that allows people with paralysis to communicate even if they are unable to speak on their own. The study appears July 15 in the New England Journal of Medicine.
“To our knowledge, this is the first successful demonstration of direct decoding of full words from the brain activity of someone who is paralyzed and cannot speak,” said Chang, the Joan and Sanford Weill Chair of Neurological Surgery at UCSF, Jeanne Robertson Distinguished Professor, and senior author on the study. “It shows strong promise to restore communication by tapping into the brain’s natural speech machinery.”
Each year, thousands of people lose the ability to speak due to stroke, accident, or disease. With further development, the approach described in this study could one day enable these people to fully communicate.
Translating Brain Signals into Speech
Previously, work in the field of communication neuroprosthetics has focused on restoring communication through spelling-based approaches to type out letters one-by-one in text. Chang’s study differs from these efforts in a critical way: his team is translating signals intended to control muscles of the vocal system for speaking words, rather than signals to move the arm or hand to enable typing. Chang said this approach taps into the natural and fluid aspects of speech and promises more rapid and organic communication.
“With speech, we normally communicate information at a very high rate, up to 150 or 200 words per minute,” he said, noting that spelling-based approaches using typing, writing, and controlling a cursor are considerably slower and more laborious. “Going straight to words, as we’re doing here, has great advantages because it’s closer to how we normally speak.”
Over the past decade, Chang’s progress toward this goal was facilitated by patients at the UCSF Epilepsy Center who were undergoing neurosurgery to pinpoint the origins of their seizures using electrode arrays placed on the surface of their brains. These patients, all of whom had normal speech, volunteered to have their brain recordings analyzed for speech-related activity. Early success with these patient volunteers paved the way for the current trial in people with paralysis.
Previously, Chang and colleagues in the UCSF Weill Institute for Neurosciences mapped the cortical activity patterns associated with vocal tract movements that produce each consonant and vowel. To translate those findings into speech recognition of full words, David Moses, PhD, a postdoctoral engineer in the Chang lab and one of the lead authors of the new study, developed new methods for real-time decoding of those patterns and statistical language models to improve accuracy.
But their success in decoding speech in participants who were able to speak didn’t guarantee that the technology would work in a person whose vocal tract is paralyzed. “Our models needed to learn the mapping between complex brain activity patterns and intended speech,” said Moses. “That poses a major challenge when the participant can’t speak.”
In addition, the team didn’t know whether brain signals controlling the vocal tract would still be intact for people who haven’t been able to move their vocal muscles for many years. “The best way to find out whether this could work was to try it,” said Moses.
The First 50 Words
To investigate the potential of this technology in patients with paralysis, Chang partnered with colleague Karunesh Ganguly, MD, PhD, an associate professor of neurology, to launch a study known as “BRAVO” (Brain-Computer Interface Restoration of Arm and Voice). The first participant in the trial is a man in his late 30s who suffered a devastating brainstem stroke more than 15 years ago that severely damaged the connection between his brain and his vocal tract and limbs. Since his injury, he has had extremely limited head, neck, and limb movements, and communicates by using a pointer attached to a baseball cap to poke letters on a screen.
The participant, who asked to be referred to as BRAVO1, worked with the researchers to create a 50-word vocabulary that Chang’s team could recognize from brain activity using advanced computer algorithms. The vocabulary — which includes words such as “water,” “family,” and “good” — was sufficient to create hundreds of sentences expressing concepts applicable to BRAVO1’s daily life.
For the study, Chang surgically implanted a high-density electrode array over BRAVO1’s speech motor cortex. After the participant’s full recovery, his team recorded 22 hours of neural activity in this brain region over 48 sessions and several months. In each session, BRAVO1 attempted to say each of the 50 vocabulary words many times while the electrodes recorded brain signals from his speech cortex.
Translating Attempted Speech into Text
To translate the patterns of recorded neural activity into specific intended words, the other two lead authors of the study, Sean Metzger, MS and Jessie Liu, BS, both bioengineering doctoral students in the Chang Lab used custom neural network models, which are forms of artificial intelligence. When the participant attempted to speak, these networks distinguished subtle patterns in brain activity to detect speech attempts and identify which words he was trying to say.
To test their approach, the team first presented BRAVO1 with short sentences constructed from the 50 vocabulary words and asked him to try saying them several times. As he made his attempts, the words were decoded from his brain activity, one by one, on a screen.
Then the team switched to prompting him with questions such as “How are you today?” and “Would you like some water?” As before, BRAVO1’s attempted speech appeared on the screen. “I am very good,” and “No, I am not thirsty.”
The team found that the system was able to decode words from brain activity at rate of up to 18 words per minute with up to 93 percent accuracy (75 percent median). Contributing to the success was a language model Moses applied that implemented an “auto-correct” function, similar to what is used by consumer texting and speech recognition software.
Moses characterized the early trial results as a proof of principle. “We were thrilled to see the accurate decoding of a variety of meaningful sentences,” he said. “We’ve shown that it is actually possible to facilitate communication in this way and that it has potential for use in conversational settings.”
Looking forward, Chang and Moses said they will expand the trial to include more participants affected by severe paralysis and communication deficits. The team is currently working to increase the number of words in the available vocabulary, as well as improve the rate of speech.
Both said that while the study focused on a single participant and a limited vocabulary, those limitations don’t diminish the accomplishment. “This is an important technological milestone for a person who cannot communicate naturally,” said Moses, “and it demonstrates the potential for this approach to give a voice to people with severe paralysis and speech loss.”
“Turning hazelnut shells into a potential renewable energy source”
Biomass is attracting growing interest from researchers as a source of renewable, sustainable, and clean energy. It can be converted into bio-oil by thermochemical methods, such as gasification, liquefaction, and pyrolysis, and used to produce fuels, chemicals, and biomaterials.
In Journal for Renewable and Sustainable Energy, researchers from Heilongjiang Academy of Agricultural Machinery Sciences in China share their work on the physicochemical properties and antioxidant activity of wood vinegar and tar fraction in bio-oil produced from hazelnut shells pyrolysis at 400 degrees Celsius to 1,000 C.
Wood vinegar is often used in agricultural fields as insect repellent, fertilizer, and plant growth promoter or inhibitor, and can be applied as an odor remover, wood preservative, and animal feed additive.
“After these results, wood vinegar and tar obtained from residual hazelnut shells could be considered as potential source of renewable energy dependent on their own characteristics,” said author Liu Xifeng.
The researchers found the wood vinegar and tar left over after burning the shells contained the most phenolic substances, which laid a foundation for the subsequent research on antioxidant properties.
The experiments were conducted in a tube furnace pyrolysis reactor, and hazelnut shells samples weighing 20 grams were placed in the waiting area of a quartz tube in advance. When the target temperature was reached and stable, the raw materials were pushed to the reaction region and heated for 20 minutes.
The biochar was determined as the ratio of pyrolytic char and biomass weight, and the bio-oil yield was calculated by the increased weight of the condenser.
To separate two fractions of bio-oil sufficiently, the liquid product was centrifuged at 3,200 revolutions per minute for eight minutes, and the aqueous fraction was called wood vinegar. The separated tar fraction remained stationary for 24 hours without the appearance of the aqueous phase.
The wood vinegar and tar were respectively stored in a sealed tube and preserved in a refrigerator at 4 C for experimental analysis, and the gas yield was calculated by considering their combined volume.
The researchers found the pyrolysis temperature had a significant effect on the yield and properties of wood vinegar and tar fraction in bio-oil obtained from hazelnut shells. Wood vinegar was the dominant liquid fraction with maximal yield of 31.23 weight percent obtained at 700 C, attributable to the high concentration of water.
This research sets the groundwork for further applications of bio-oil from waste hazelnut shell pyrolysis, and its application in antioxidant activity has been extended.